Limelight Unveils GraphQL Functionality for Its Layer0 Web Application CDN

posted on December 15, 2021

tags:

Content delivery services and AppOps at the edge provider, Limelight Networks (Nasdaq: LLNW), has announced general availability of GraphQL functionality for its ‘Layer0 by Limelight’ web application CDN.

Rust, Brave Search, and What’s Next in JavaScript | Cloud Chats: Episode 35

posted on October 29, 2021

tags:

Catch the latest developer news, watch tech demos, play a game, and ask us anything in this week’s Cloud Chats: “Rust, Brave Search, and What’s Next in JavaScript.” Co-hosts from DigitalOcean: Kim Schlesinger, Developer Advocate Matt Cowley, Community Platform Manager Chris Sev, Senior Developer Advocate, Mason Egger, Senior Developer Advocate – – – – – […]

What are the top 4 programming languages in demand in America?

posted on June 6, 2021

tags:

From what we’ve seen in terms of # of job opportunities:

  • Javascript: Not my favorite language, but it’s extremely versatile, and in use for both frontend and backend systems now that node.js has gained a lot of momentum. Lots of libraries to do almost anything. Even things that you shouldn’t need a JS library to do.
  • Python: It’s been around a while, it’s easy to learn, quite powerful at manipulating data, and has a great deal of academic library support for doing things like Machine Learning, AI, NLP, etc.
  • Java: It isn’t the greatest language, but at one point in time it was at the top of the pile. The language spec has stagnated, but there is a lot of code in production still written in and using Java. It also is useful if you’re going into Android development.
  • .NET: The MS version of Java, and now with Core/Standard support, it can run on almost any platform, not just windows devices. Its language evolves at a much more rapid pace than Java, and there’s a lot of support out there from the community.

What is the easiest JavaScript framework to learn?

posted on June 4, 2021

tags:

JavaScript is the foundation of web development, while JS developers are always in high demand. JS frameworks are sets of pre-written JavaScript code that are used to simplify and increase the efficiency of the development process.

There are no straightforward frameworks, but if you wonder which one will be easier to learn, I recommend Vue. js. Many JavaScript professionals consider Vue as a reliable option, ideal for new JavaScript developers.

Vue has very detailed documentation which:

- speeds up the learning process for developers;

- saves time on application development.

You can integrate Vue into any JS project to develop an interface. Besides, you can use different JS infrastructure simultaneously to create complex front-end solutions.

You also have to learn how to use React.js. React is technically a JavaScript library. It has, for many years, been the top popular JavaScript framework.

The React ecosystem allows you to adapt the application for many devices and experiment with the interface. Also, this framework supports mobile development.

On top of that, if you know React, you can quickly learn the infrastructure for hybrid mobile development. Versatility and flexibility are the most significant advantages of this framework.

What are the benefits of using Node.js?

posted on June 3, 2021

tags:

Node.js is an open-source, cross-platform JavaScript environment that helps in real-time network application development. To ensure outstanding efficiency, it employs a non-blocking I / O paradigm. In recent years, Node.js has gained considerable popularity in the development community.

Let's look at the main advantages of using Node.js.

1. Simple scalability. Applications can scale horizontally by adding additional nodes to an existing system.

2. Node.js is used as a single programming language.

3. Node.js offers high performance.

4. Node.js has a large and active community of developers. They are continually contributing to further development and improvement.

5. Node.js provides the ability to process multiple requests simultaneously.

6. Node.js is especially useful for reducing time to market.

Of course, Node.js is a mature and well-tested tool that will not be neglected or abandoned shortly.

JavaScript Tutorial

posted on May 30, 2021

tags:

What is JavaScript ?

JavaScript is a dynamic computer programming language. It is lightweight and most commonly used as a part of web pages, whose implementations allow client-side script to interact with the user and make dynamic pages. It is an interpreted programming language with object-oriented capabilities.

JavaScript was first known as LiveScript, but Netscape changed its name to JavaScript, possibly because of the excitement being generated by Java. JavaScript made its first appearance in Netscape 2.0 in 1995 with the name LiveScript. The general-purpose core of the language has been embedded in Netscape, Internet Explorer, and other web browsers.

The ECMA-262 Specification defined a standard version of the core JavaScript language.

  • JavaScript is a lightweight, interpreted programming language.
  • Designed for creating network-centric applications.
  • Complementary to and integrated with Java.
  • Complementary to and integrated with HTML.
  • Open and cross-platform

Client-Side JavaScript

Client-side JavaScript is the most common form of the language. The script should be included in or referenced by an HTML document for the code to be interpreted by the browser.

It means that a web page need not be a static HTML, but can include programs that interact with the user, control the browser, and dynamically create HTML content.

The JavaScript client-side mechanism provides many advantages over traditional CGI server-side scripts. For example, you might use JavaScript to check if the user has entered a valid e-mail address in a form field.

The JavaScript code is executed when the user submits the form, and only if all the entries are valid, they would be submitted to the Web Server.

JavaScript can be used to trap user-initiated events such as button clicks, link navigation, and other actions that the user initiates explicitly or implicitly.

Advantages of JavaScript

The merits of using JavaScript are −

  • Less server interaction − You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.

  • Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something.

  • Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.

  • Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.

Limitations of JavaScript

We cannot treat JavaScript as a full-fledged programming language. It lacks the following important features −

  • Client-side JavaScript does not allow the reading or writing of files. This has been kept for security reason.

  • JavaScript cannot be used for networking applications because there is no such support available.

  • JavaScript doesn't have any multi-threading or multiprocessor capabilities.

Once again, JavaScript is a lightweight, interpreted programming language that allows you to build interactivity into otherwise static HTML pages.

JavaScript Development Tools

One of major strengths of JavaScript is that it does not require expensive development tools. You can start with a simple text editor such as Notepad. Since it is an interpreted language inside the context of a web browser, you don't even need to buy a compiler.

To make our life simpler, various vendors have come up with very nice JavaScript editing tools. Some of them are listed here −

  • Microsoft FrontPage − Microsoft has developed a popular HTML editor called FrontPage. FrontPage also provides web developers with a number of JavaScript tools to assist in the creation of interactive websites.

  • Macromedia Dreamweaver MX − Macromedia Dreamweaver MX is a very popular HTML and JavaScript editor in the professional web development crowd. It provides several handy prebuilt JavaScript components, integrates well with databases, and conforms to new standards such as XHTML and XML.

  • Macromedia HomeSite 5 − HomeSite 5 is a well-liked HTML and JavaScript editor from Macromedia that can be used to manage personal websites effectively.

Where is JavaScript Today ?

The ECMAScript Edition 5 standard will be the first update to be released in over four years. JavaScript 2.0 conforms to Edition 5 of the ECMAScript standard, and the difference between the two is extremely minor.

The specification for JavaScript 2.0 can be found on the following site: http://www.ecmascript.org/

Today, Netscape's JavaScript and Microsoft's JScript conform to the ECMAScript standard, although both the languages still support the features that are not a part of the standard.

JavaScript - Syntax

JavaScript can be implemented using JavaScript statements that are placed within the <script>... </script> HTML tags in a web page.

You can place the <script> tags, containing your JavaScript, anywhere within your web page, but it is normally recommended that you should keep it within the <head> tags.

The <script> tag alerts the browser program to start interpreting all the text between these tags as a script. A simple syntax of your JavaScript will appear as follows.

<script ...>
   JavaScript code
</script>

The script tag takes two important attributes −

  • Language − This attribute specifies what scripting language you are using. Typically, its value will be javascript. Although recent versions of HTML (and XHTML, its successor) have phased out the use of this attribute.

  • Type − This attribute is what is now recommended to indicate the scripting language in use and its value should be set to "text/javascript".

So your JavaScript segment will look like −

<script language = "javascript" type = "text/javascript">
   JavaScript code
</script>

Your First JavaScript Code

Let us take a sample example to print out "Hello World". We added an optional HTML comment that surrounds our JavaScript code. This is to save our code from a browser that does not support JavaScript. The comment ends with a "//-->". Here "//" signifies a comment in JavaScript, so we add that to prevent a browser from reading the end of the HTML comment as a piece of JavaScript code. Next, we call a function document.write which writes a string into our HTML document.

This function can be used to write text, HTML, or both. Take a look at the following code.

Live Demo
<html>
   <body>   
      <script language = "javascript" type = "text/javascript">
         <!--
            document.write("Hello World!")
         //-->
      </script>      
   </body>
</html>

This code will produce the following result −

Hello World!

Whitespace and Line Breaks

JavaScript ignores spaces, tabs, and newlines that appear in JavaScript programs. You can use spaces, tabs, and newlines freely in your program and you are free to format and indent your programs in a neat and consistent way that makes the code easy to read and understand.

Semicolons are Optional

Simple statements in JavaScript are generally followed by a semicolon character, just as they are in C, C++, and Java. JavaScript, however, allows you to omit this semicolon if each of your statements are placed on a separate line. For example, the following code could be written without semicolons.

<script language = "javascript" type = "text/javascript">
   <!--
      var1 = 10
      var2 = 20
   //-->
</script>

But when formatted in a single line as follows, you must use semicolons −

<script language = "javascript" type = "text/javascript">
   <!--
      var1 = 10; var2 = 20;
   //-->
</script>

Note − It is a good programming practice to use semicolons.

Case Sensitivity

JavaScript is a case-sensitive language. This means that the language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.

So the identifiers Time and TIME will convey different meanings in JavaScript.

NOTE − Care should be taken while writing variable and function names in JavaScript.

Comments in JavaScript

JavaScript supports both C-style and C++-style comments, Thus −

  • Any text between a // and the end of a line is treated as a comment and is ignored by JavaScript.

  • Any text between the characters /* and */ is treated as a comment. This may span multiple lines.

  • JavaScript also recognizes the HTML comment opening sequence <!--. JavaScript treats this as a single-line comment, just as it does the // comment.

  • The HTML comment closing sequence --> is not recognized by JavaScript so it should be written as //-->.

Example

The following example shows how to use comments in JavaScript.

<script language = "javascript" type = "text/javascript">
   <!--
      // This is a comment. It is similar to comments in C++
   
      /*
      * This is a multi-line comment in JavaScript
      * It is very similar to comments in C Programming
      */
   //-->
</script>

Enabling JavaScript in Browsers

All the modern browsers come with built-in support for JavaScript. Frequently, you may need to enable or disable this support manually. This chapter explains the procedure of enabling and disabling JavaScript support in your browsers: Internet Explorer, Firefox, chrome, and Opera.

JavaScript in Internet Explorer

Here are simple steps to turn on or turn off JavaScript in your Internet Explorer −

  • Follow Tools → Internet Options from the menu.

  • Select Security tab from the dialog box.

  • Click the Custom Level button.

  • Scroll down till you find Scripting option.

  • Select Enable radio button under Active scripting.

  • Finally click OK and come out

To disable JavaScript support in your Internet Explorer, you need to select Disable radio button under Active scripting.

JavaScript in Firefox

Here are the steps to turn on or turn off JavaScript in Firefox −

  • Open a new tab → type about: config in the address bar.

  • Then you will find the warning dialog. Select I’ll be careful, I promise!

  • Then you will find the list of configure options in the browser.

  • In the search bar, type javascript.enabled.

  • There you will find the option to enable or disable javascript by right-clicking on the value of that option → select toggle.

If javascript.enabled is true; it converts to false upon clicking toogle. If javascript is disabled; it gets enabled upon clicking toggle.

JavaScript in Chrome

Here are the steps to turn on or turn off JavaScript in Chrome −

  • Click the Chrome menu at the top right hand corner of your browser.

  • Select Settings.

  • Click Show advanced settings at the end of the page.

  • Under the Privacy section, click the Content settings button.

  • In the "Javascript" section, select "Do not allow any site to run JavaScript" or "Allow all sites to run JavaScript (recommended)".

JavaScript in Opera

Here are the steps to turn on or turn off JavaScript in Opera −

  • Follow Tools → Preferences from the menu.

  • Select Advanced option from the dialog box.

  • Select Content from the listed items.

  • Select Enable JavaScript checkbox.

  • Finally click OK and come out.

To disable JavaScript support in your Opera, you should not select the Enable JavaScript checkbox.

Warning for Non-JavaScript Browsers

If you have to do something important using JavaScript, then you can display a warning message to the user using <noscript> tags.

You can add a noscript block immediately after the script block as follows −

<html>
   <body>
      <script language = "javascript" type = "text/javascript">
         <!--
            document.write("Hello World!")
         //-->
      </script>
      
      <noscript>
         Sorry...JavaScript is needed to go ahead.
      </noscript>      
   </body>
</html>

Now, if the user's browser does not support JavaScript or JavaScript is not enabled, then the message from </noscript> will be displayed on the screen.

JavaScript - Placement in HTML File

There is a flexibility given to include JavaScript code anywhere in an HTML document. However the most preferred ways to include JavaScript in an HTML file are as follows −

  • Script in <head>...</head> section.

  • Script in <body>...</body> section.

  • Script in <body>...</body> and <head>...</head> sections.

  • Script in an external file and then include in <head>...</head> section.

In the following section, we will see how we can place JavaScript in an HTML file in different ways.

JavaScript in <head>...</head> section

If you want to have a script run on some event, such as when a user clicks somewhere, then you will place that script in the head as follows −

Live Demo
<html>
   <head>      
      <script type = "text/javascript">
         <!--
            function sayHello() {
               alert("Hello World")
            }
         //-->
      </script>     
   </head>
   
   <body>
      <input type = "button" onclick = "sayHello()" value = "Say Hello" />
   </body>  
</html>

This code will produce the following results −

JavaScript in <body>...</body> section

If you need a script to run as the page loads so that the script generates content in the page, then the script goes in the <body> portion of the document. In this case, you would not have any function defined using JavaScript. Take a look at the following code.

Live Demo
<html>
   <head>
   </head>
   
   <body>
      <script type = "text/javascript">
         <!--
            document.write("Hello World")
         //-->
      </script>
      
      <p>This is web page body </p>
   </body>
</html>

This code will produce the following results −

JavaScript in <body> and <head> Sections

You can put your JavaScript code in <head> and <body> section altogether as follows −

Live Demo
<html>
   <head>
      <script type = "text/javascript">
         <!--
            function sayHello() {
               alert("Hello World")
            }
         //-->
      </script>
   </head>
   
   <body>
      <script type = "text/javascript">
         <!--
            document.write("Hello World")
         //-->
      </script>
      
      <input type = "button" onclick = "sayHello()" value = "Say Hello" />
   </body>
</html>

This code will produce the following result −

JavaScript in External File

As you begin to work more extensively with JavaScript, you will be likely to find that there are cases where you are reusing identical JavaScript code on multiple pages of a site.

You are not restricted to be maintaining identical code in multiple HTML files. The script tag provides a mechanism to allow you to store JavaScript in an external file and then include it into your HTML files.

Here is an example to show how you can include an external JavaScript file in your HTML code using script tag and its src attribute.

<html>
   <head>
      <script type = "text/javascript" src = "filename.js" ></script>
   </head>
   
   <body>
      .......
   </body>
</html>

To use JavaScript from an external file source, you need to write all your JavaScript source code in a simple text file with the extension ".js" and then include that file as shown above.

For example, you can keep the following content in filename.js file and then you can use sayHello function in your HTML file after including the filename.js file.

function sayHello() {
   alert("Hello World")
}

JavaScript - Variables

JavaScript Datatypes

One of the most fundamental characteristics of a programming language is the set of data types it supports. These are the type of values that can be represented and manipulated in a programming language.

JavaScript allows you to work with three primitive data types −

  • Numbers, eg. 123, 120.50 etc.

  • Strings of text e.g. "This text string" etc.

  • Boolean e.g. true or false.

JavaScript also defines two trivial data types, null and undefined, each of which defines only a single value. In addition to these primitive data types, JavaScript supports a composite data type known as object. We will cover objects in detail in a separate chapter.

Note − JavaScript does not make a distinction between integer values and floating-point values. All numbers in JavaScript are represented as floating-point values. JavaScript represents numbers using the 64-bit floating-point format defined by the IEEE 754 standard.

JavaScript Variables

Like many other programming languages, JavaScript has variables. Variables can be thought of as named containers. You can place data into these containers and then refer to the data simply by naming the container.

Before you use a variable in a JavaScript program, you must declare it. Variables are declared with the var keyword as follows.

<script type = "text/javascript">
   <!--
      var money;
      var name;
   //-->
</script>

You can also declare multiple variables with the same var keyword as follows −

<script type = "text/javascript">
   <!--
      var money, name;
   //-->
</script>

Storing a value in a variable is called variable initialization. You can do variable initialization at the time of variable creation or at a later point in time when you need that variable.

For instance, you might create a variable named money and assign the value 2000.50 to it later. For another variable, you can assign a value at the time of initialization as follows.

<script type = "text/javascript">
   <!--
      var name = "Ali";
      var money;
      money = 2000.50;
   //-->
</script>

Note − Use the var keyword only for declaration or initialization, once for the life of any variable name in a document. You should not re-declare same variable twice.

JavaScript is untyped language. This means that a JavaScript variable can hold a value of any data type. Unlike many other languages, you don't have to tell JavaScript during variable declaration what type of value the variable will hold. The value type of a variable can change during the execution of a program and JavaScript takes care of it automatically.

JavaScript Variable Scope

The scope of a variable is the region of your program in which it is defined. JavaScript variables have only two scopes.

  • Global Variables − A global variable has global scope which means it can be defined anywhere in your JavaScript code.

  • Local Variables − A local variable will be visible only within a function where it is defined. Function parameters are always local to that function.

Within the body of a function, a local variable takes precedence over a global variable with the same name. If you declare a local variable or function parameter with the same name as a global variable, you effectively hide the global variable. Take a look into the following example.

Live Demo
<html>
   <body onload = checkscope();>   
      <script type = "text/javascript">
         <!--
            var myVar = "global";      // Declare a global variable
            function checkscope( ) {
               var myVar = "local";    // Declare a local variable
               document.write(myVar);
            }
         //-->
      </script>     
   </body>
</html>

This produces the following result −

local

JavaScript Variable Names

While naming your variables in JavaScript, keep the following rules in mind.

  • You should not use any of the JavaScript reserved keywords as a variable name. These keywords are mentioned in the next section. For example, break or boolean variable names are not valid.

  • JavaScript variable names should not start with a numeral (0-9). They must begin with a letter or an underscore character. For example, 123test is an invalid variable name but _123test is a valid one.

  • JavaScript variable names are case-sensitive. For example, Name and name are two different variables.

JavaScript Reserved Words

A list of all the reserved words in JavaScript are given in the following table. They cannot be used as JavaScript variables, functions, methods, loop labels, or any object names.

abstract else instanceof switch
boolean enum int synchronized
break export interface this
byte extends long throw
case false native throws
catch final new transient
char finally null true
class float package try
const for private typeof
continue function protected var
debugger goto public void
default if return volatile
delete implements short while
do import static with
double in super

JavaScript - Operators

What is an Operator?

Let us take a simple expression 4 + 5 is equal to 9. Here 4 and 5 are called operands and ‘+’ is called the operator. JavaScript supports the following types of operators.

  • Arithmetic Operators
  • Comparison Operators
  • Logical (or Relational) Operators
  • Assignment Operators
  • Conditional (or ternary) Operators

Lets have a look on all operators one by one.

Arithmetic Operators

JavaScript supports the following arithmetic operators −

Assume variable A holds 10 and variable B holds 20, then −

Sr.No. Operator & Description
1

+ (Addition)

Adds two operands

Ex: A + B will give 30

2

- (Subtraction)

Subtracts the second operand from the first

Ex: A - B will give -10

3

* (Multiplication)

Multiply both operands

Ex: A * B will give 200

4

/ (Division)

Divide the numerator by the denominator

Ex: B / A will give 2

5

% (Modulus)

Outputs the remainder of an integer division

Ex: B % A will give 0

6

++ (Increment)

Increases an integer value by one

Ex: A++ will give 11

7

-- (Decrement)

Decreases an integer value by one

Ex: A-- will give 9

Note − Addition operator (+) works for Numeric as well as Strings. e.g. "a" + 10 will give "a10".

Example

The following code shows how to use arithmetic operators in JavaScript.

Live Demo
<html>
   <body>
   
      <script type = "text/javascript">
         <!--
            var a = 33;
            var b = 10;
            var c = "Test";
            var linebreak = "<br />";
         
            document.write("a + b = ");
            result = a + b;
            document.write(result);
            document.write(linebreak);
         
            document.write("a - b = ");
            result = a - b;
            document.write(result);
            document.write(linebreak);
         
            document.write("a / b = ");
            result = a / b;
            document.write(result);
            document.write(linebreak);
         
            document.write("a % b = ");
            result = a % b;
            document.write(result);
            document.write(linebreak);
         
            document.write("a + b + c = ");
            result = a + b + c;
            document.write(result);
            document.write(linebreak);
         
            a = ++a;
            document.write("++a = ");
            result = ++a;
            document.write(result);
            document.write(linebreak);
         
            b = --b;
            document.write("--b = ");
            result = --b;
            document.write(result);
            document.write(linebreak);
         //-->
      </script>
      
      Set the variables to different values and then try...
   </body>
</html>

Output

a + b = 43
a - b = 23
a / b = 3.3
a % b = 3
a + b + c = 43Test
++a = 35
--b = 8
Set the variables to different values and then try...

Comparison Operators

JavaScript supports the following comparison operators −

Assume variable A holds 10 and variable B holds 20, then −

Sr.No. Operator & Description
1

= = (Equal)

Checks if the value of two operands are equal or not, if yes, then the condition becomes true.

Ex: (A == B) is not true.

2

!= (Not Equal)

Checks if the value of two operands are equal or not, if the values are not equal, then the condition becomes true.

Ex: (A != B) is true.

3

> (Greater than)

Checks if the value of the left operand is greater than the value of the right operand, if yes, then the condition becomes true.

Ex: (A > B) is not true.

4

< (Less than)

Checks if the value of the left operand is less than the value of the right operand, if yes, then the condition becomes true.

Ex: (A < B) is true.

5

>= (Greater than or Equal to)

Checks if the value of the left operand is greater than or equal to the value of the right operand, if yes, then the condition becomes true.

Ex: (A >= B) is not true.

6

<= (Less than or Equal to)

Checks if the value of the left operand is less than or equal to the value of the right operand, if yes, then the condition becomes true.

Ex: (A <= B) is true.

Example

The following code shows how to use comparison operators in JavaScript.

Live Demo
<html>
   <body>  
      <script type = "text/javascript">
         <!--
            var a = 10;
            var b = 20;
            var linebreak = "<br />";
      
            document.write("(a == b) => ");
            result = (a == b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a < b) => ");
            result = (a < b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a > b) => ");
            result = (a > b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a != b) => ");
            result = (a != b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a >= b) => ");
            result = (a >= b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a <= b) => ");
            result = (a <= b);
            document.write(result);
            document.write(linebreak);
         //-->
      </script>      
      Set the variables to different values and different operators and then try...
   </body>
</html>

Output

(a == b) => false 
(a < b) => true 
(a > b) => false 
(a != b) => true 
(a >= b) => false 
a <= b) => true
Set the variables to different values and different operators and then try...

Logical Operators

JavaScript supports the following logical operators −

Assume variable A holds 10 and variable B holds 20, then −

Sr.No. Operator & Description
1

&& (Logical AND)

If both the operands are non-zero, then the condition becomes true.

Ex: (A && B) is true.

2

|| (Logical OR)

If any of the two operands are non-zero, then the condition becomes true.

Ex: (A || B) is true.

3

! (Logical NOT)

Reverses the logical state of its operand. If a condition is true, then the Logical NOT operator will make it false.

Ex: ! (A && B) is false.

Example

Try the following code to learn how to implement Logical Operators in JavaScript.

Live Demo
<html>
   <body>   
      <script type = "text/javascript">
         <!--
            var a = true;
            var b = false;
            var linebreak = "<br />";
      
            document.write("(a && b) => ");
            result = (a && b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a || b) => ");
            result = (a || b);
            document.write(result);
            document.write(linebreak);
         
            document.write("!(a && b) => ");
            result = (!(a && b));
            document.write(result);
            document.write(linebreak);
         //-->
      </script>      
      <p>Set the variables to different values and different operators and then try...</p>
   </body>
</html>

Output

(a && b) => false 
(a || b) => true 
!(a && b) => true
Set the variables to different values and different operators and then try...

Bitwise Operators

JavaScript supports the following bitwise operators −

Assume variable A holds 2 and variable B holds 3, then −

Sr.No. Operator & Description
1

& (Bitwise AND)

It performs a Boolean AND operation on each bit of its integer arguments.

Ex: (A & B) is 2.

2

| (BitWise OR)

It performs a Boolean OR operation on each bit of its integer arguments.

Ex: (A | B) is 3.

3

^ (Bitwise XOR)

It performs a Boolean exclusive OR operation on each bit of its integer arguments. Exclusive OR means that either operand one is true or operand two is true, but not both.

Ex: (A ^ B) is 1.

4

~ (Bitwise Not)

It is a unary operator and operates by reversing all the bits in the operand.

Ex: (~B) is -4.

5

<< (Left Shift)

It moves all the bits in its first operand to the left by the number of places specified in the second operand. New bits are filled with zeros. Shifting a value left by one position is equivalent to multiplying it by 2, shifting two positions is equivalent to multiplying by 4, and so on.

Ex: (A << 1) is 4.

6

>> (Right Shift)

Binary Right Shift Operator. The left operand’s value is moved right by the number of bits specified by the right operand.

Ex: (A >> 1) is 1.

7

>>> (Right shift with Zero)

This operator is just like the >> operator, except that the bits shifted in on the left are always zero.

Ex: (A >>> 1) is 1.

Example

Try the following code to implement Bitwise operator in JavaScript.

Live Demo
<html>
   <body>   
      <script type = "text/javascript">
         <!--
            var a = 2; // Bit presentation 10
            var b = 3; // Bit presentation 11
            var linebreak = "<br />";
         
            document.write("(a & b) => ");
            result = (a & b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a | b) => ");
            result = (a | b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a ^ b) => ");
            result = (a ^ b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(~b) => ");
            result = (~b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a << b) => ");
            result = (a << b);
            document.write(result);
            document.write(linebreak);
         
            document.write("(a >> b) => ");
            result = (a >> b);
            document.write(result);
            document.write(linebreak);
         //-->
      </script>      
      <p>Set the variables to different values and different operators and then try...</p>
   </body>
</html>
(a & b) => 2 
(a | b) => 3 
(a ^ b) => 1 
(~b) => -4 
(a << b) => 16 
(a >> b) => 0
Set the variables to different values and different operators and then try...

Assignment Operators

JavaScript supports the following assignment operators −

Sr.No. Operator & Description
1

= (Simple Assignment )

Assigns values from the right side operand to the left side operand

Ex: C = A + B will assign the value of A + B into C

2

+= (Add and Assignment)

It adds the right operand to the left operand and assigns the result to the left operand.

Ex: C += A is equivalent to C = C + A

3

−= (Subtract and Assignment)

It subtracts the right operand from the left operand and assigns the result to the left operand.

Ex: C -= A is equivalent to C = C - A

4

*= (Multiply and Assignment)

It multiplies the right operand with the left operand and assigns the result to the left operand.

Ex: C *= A is equivalent to C = C * A

5

/= (Divide and Assignment)

It divides the left operand with the right operand and assigns the result to the left operand.

Ex: C /= A is equivalent to C = C / A

6

%= (Modules and Assignment)

It takes modulus using two operands and assigns the result to the left operand.

Ex: C %= A is equivalent to C = C % A

Note − Same logic applies to Bitwise operators so they will become like <<=, >>=, >>=, &=, |= and ^=.

Example

Try the following code to implement assignment operator in JavaScript.

Live Demo
<html>
   <body>   
      <script type = "text/javascript">
         <!--
            var a = 33;
            var b = 10;
            var linebreak = "<br />";
         
            document.write("Value of a => (a = b) => ");
            result = (a = b);
            document.write(result);
            document.write(linebreak);
         
            document.write("Value of a => (a += b) => ");
            result = (a += b);
            document.write(result);
            document.write(linebreak);
         
            document.write("Value of a => (a -= b) => ");
            result = (a -= b);
            document.write(result);
            document.write(linebreak);
         
            document.write("Value of a => (a *= b) => ");
            result = (a *= b);
            document.write(result);
            document.write(linebreak);
         
            document.write("Value of a => (a /= b) => ");
            result = (a /= b);
            document.write(result);
            document.write(linebreak);
         
            document.write("Value of a => (a %= b) => ");
            result = (a %= b);
            document.write(result);
            document.write(linebreak);
         //-->
      </script>      
      <p>Set the variables to different values and different operators and then try...</p>
   </body>
</html>

Output

Value of a => (a = b) => 10
Value of a => (a += b) => 20 
Value of a => (a -= b) => 10 
Value of a => (a *= b) => 100 
Value of a => (a /= b) => 10
Value of a => (a %= b) => 0
Set the variables to different values and different operators and then try...

Miscellaneous Operator

We will discuss two operators here that are quite useful in JavaScript: the conditional operator (? :) and the typeof operator.

Conditional Operator (? :)

The conditional operator first evaluates an expression for a true or false value and then executes one of the two given statements depending upon the result of the evaluation.

Sr.No. Operator and Description
1

? : (Conditional )

If Condition is true? Then value X : Otherwise value Y

Example

Try the following code to understand how the Conditional Operator works in JavaScript.

Live Demo
<html>
   <body>   
      <script type = "text/javascript">
         <!--
            var a = 10;
            var b = 20;
            var linebreak = "<br />";
         
            document.write ("((a > b) ? 100 : 200) => ");
            result = (a > b) ? 100 : 200;
            document.write(result);
            document.write(linebreak);
         
            document.write ("((a < b) ? 100 : 200) => ");
            result = (a < b) ? 100 : 200;
            document.write(result);
            document.write(linebreak);
         //-->
      </script>      
      <p>Set the variables to different values and different operators and then try...</p>
   </body>
</html>

Output

((a > b) ? 100 : 200) => 200 
((a < b) ? 100 : 200) => 100
Set the variables to different values and different operators and then try...

typeof Operator

The typeof operator is a unary operator that is placed before its single operand, which can be of any type. Its value is a string indicating the data type of the operand.

The typeof operator evaluates to "number", "string", or "boolean" if its operand is a number, string, or boolean value and returns true or false based on the evaluation.

Here is a list of the return values for the typeof Operator.

Type String Returned by typeof
Number "number"
String "string"
Boolean "boolean"
Object "object"
Function "function"
Undefined "undefined"
Null "object"

Example

The following code shows how to implement typeof operator.

Live Demo
<html>
   <body>      
      <script type = "text/javascript">
         <!--
            var a = 10;
            var b = "String";
            var linebreak = "<br />";
         
            result = (typeof b == "string" ? "B is String" : "B is Numeric");
            document.write("Result => ");
            document.write(result);
            document.write(linebreak);
         
            result = (typeof a == "string" ? "A is String" : "A is Numeric");
            document.write("Result => ");
            document.write(result);
            document.write(linebreak);
         //-->
      </script>      
      <p>Set the variables to different values and different operators and then try...</p>
   </body>
</html>

Output

Result => B is String 
Result => A is Numeric
Set the variables to different values and different operators and then try...

JavaScript - if...else Statement

While writing a program, there may be a situation when you need to adopt one out of a given set of paths. In such cases, you need to use conditional statements that allow your program to make correct decisions and perform right actions.

JavaScript supports conditional statements which are used to perform different actions based on different conditions. Here we will explain the if..else statement.

Flow Chart of if-else

The following flow chart shows how the if-else statement works.

Decision Making

JavaScript supports the following forms of if..else statement −

  • if statement

  • if...else statement

  • if...else if... statement.

if statement

The if statement is the fundamental control statement that allows JavaScript to make decisions and execute statements conditionally.

Syntax

The syntax for a basic if statement is as follows −

if (expression) {
   Statement(s) to be executed if expression is true
}

Here a JavaScript expression is evaluated. If the resulting value is true, the given statement(s) are executed. If the expression is false, then no statement would be not executed. Most of the times, you will use comparison operators while making decisions.

Example

Try the following example to understand how the if statement works.

Live Demo
<html>
   <body>     
      <script type = "text/javascript">
         <!--
            var age = 20;
         
            if( age > 18 ) {
               document.write("<b>Qualifies for driving</b>");
            }
         //-->
      </script>      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Qualifies for driving
Set the variable to different value and then try...

if...else statement

The 'if...else' statement is the next form of control statement that allows JavaScript to execute statements in a more controlled way.

Syntax

if (expression) {
   Statement(s) to be executed if expression is true
} else {
   Statement(s) to be executed if expression is false
}

Here JavaScript expression is evaluated. If the resulting value is true, the given statement(s) in the ‘if’ block, are executed. If the expression is false, then the given statement(s) in the else block are executed.

Example

Try the following code to learn how to implement an if-else statement in JavaScript.

Live Demo
<html>
   <body>   
      <script type = "text/javascript">
         <!--
            var age = 15;
         
            if( age > 18 ) {
               document.write("<b>Qualifies for driving</b>");
            } else {
               document.write("<b>Does not qualify for driving</b>");
            }
         //-->
      </script>     
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Does not qualify for driving
Set the variable to different value and then try...

if...else if... statement

The if...else if... statement is an advanced form of if…else that allows JavaScript to make a correct decision out of several conditions.

Syntax

The syntax of an if-else-if statement is as follows −

if (expression 1) {
   Statement(s) to be executed if expression 1 is true
} else if (expression 2) {
   Statement(s) to be executed if expression 2 is true
} else if (expression 3) {
   Statement(s) to be executed if expression 3 is true
} else {
   Statement(s) to be executed if no expression is true
}

There is nothing special about this code. It is just a series of if statements, where each if is a part of the else clause of the previous statement. Statement(s) are executed based on the true condition, if none of the conditions is true, then the else block is executed.

Example

Try the following code to learn how to implement an if-else-if statement in JavaScript.

Live Demo
<html>
   <body>   
      <script type = "text/javascript">
         <!--
            var book = "maths";
            if( book == "history" ) {
               document.write("<b>History Book</b>");
            } else if( book == "maths" ) {
               document.write("<b>Maths Book</b>");
            } else if( book == "economics" ) {
               document.write("<b>Economics Book</b>");
            } else {
               document.write("<b>Unknown Book</b>");
            }
         //-->
      </script>      
      <p>Set the variable to different value and then try...</p>
   </body>
<html>

Output

Maths Book
Set the variable to different value and then try...

JavaScript - Switch Case

You can use multiple if...else…if statements, as in the previous chapter, to perform a multiway branch. However, this is not always the best solution, especially when all of the branches depend on the value of a single variable.

Starting with JavaScript 1.2, you can use a switch statement which handles exactly this situation, and it does so more efficiently than repeated if...else if statements.

Flow Chart

The following flow chart explains a switch-case statement works.

Switch case

Syntax

The objective of a switch statement is to give an expression to evaluate and several different statements to execute based on the value of the expression. The interpreter checks each case against the value of the expression until a match is found. If nothing matches, a default condition will be used.

switch (expression) {
   case condition 1: statement(s)
   break;
   
   case condition 2: statement(s)
   break;
   ...
   
   case condition n: statement(s)
   break;
   
   default: statement(s)
}

The break statements indicate the end of a particular case. If they were omitted, the interpreter would continue executing each statement in each of the following cases.

We will explain break statement in Loop Control chapter.

Example

Try the following example to implement switch-case statement.

Live Demo
<html>
   <body>   
      <script type = "text/javascript">
         <!--
            var grade = 'A';
            document.write("Entering switch block<br />");
            switch (grade) {
               case 'A': document.write("Good job<br />");
               break;
            
               case 'B': document.write("Pretty good<br />");
               break;
            
               case 'C': document.write("Passed<br />");
               break;
            
               case 'D': document.write("Not so good<br />");
               break;
            
               case 'F': document.write("Failed<br />");
               break;
            
               default:  document.write("Unknown grade<br />")
            }
            document.write("Exiting switch block");
         //-->
      </script>      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Entering switch block
Good job
Exiting switch block
Set the variable to different value and then try...

Break statements play a major role in switch-case statements. Try the following code that uses switch-case statement without any break statement.

Live Demo
<html>
   <body>      
      <script type = "text/javascript">
         <!--
            var grade = 'A';
            document.write("Entering switch block<br />");
            switch (grade) {
               case 'A': document.write("Good job<br />");
               case 'B': document.write("Pretty good<br />");
               case 'C': document.write("Passed<br />");
               case 'D': document.write("Not so good<br />");
               case 'F': document.write("Failed<br />");
               default: document.write("Unknown grade<br />")
            }
            document.write("Exiting switch block");
         //-->
      </script>      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Entering switch block
Good job
Pretty good
Passed
Not so good
Failed
Unknown grade
Exiting switch block
Set the variable to different value and then try...

JavaScript - While Loops

While writing a program, you may encounter a situation where you need to perform an action over and over again. In such situations, you would need to write loop statements to reduce the number of lines.

JavaScript supports all the necessary loops to ease down the pressure of programming.

The while Loop

The most basic loop in JavaScript is the while loop which would be discussed in this chapter. The purpose of a while loop is to execute a statement or code block repeatedly as long as an expression is true. Once the expression becomes false, the loop terminates.

Flow Chart

The flow chart of while loop looks as follows −

While loop

Syntax

The syntax of while loop in JavaScript is as follows −

while (expression) {
   Statement(s) to be executed if expression is true
}

Example

Try the following example to implement while loop.

Live Demo
<html>
   <body>
      
      <script type = "text/javascript">
         <!--
            var count = 0;
            document.write("Starting Loop ");
         
            while (count < 10) {
               document.write("Current Count : " + count + "<br />");
               count++;
            }
         
            document.write("Loop stopped!");
         //-->
      </script>
      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Starting Loop
Current Count : 0
Current Count : 1
Current Count : 2
Current Count : 3
Current Count : 4
Current Count : 5
Current Count : 6
Current Count : 7
Current Count : 8
Current Count : 9
Loop stopped!
Set the variable to different value and then try... 

The do...while Loop

The do...while loop is similar to the while loop except that the condition check happens at the end of the loop. This means that the loop will always be executed at least once, even if the condition is false.

Flow Chart

The flow chart of a do-while loop would be as follows −

Do While Loop

Syntax

The syntax for do-while loop in JavaScript is as follows −

do {
   Statement(s) to be executed;
} while (expression);

Note − Don’t miss the semicolon used at the end of the do...while loop.

Example

Try the following example to learn how to implement a do-while loop in JavaScript.

Live Demo
<html>
   <body>   
      <script type = "text/javascript">
         <!--
            var count = 0;
            
            document.write("Starting Loop" + "<br />");
            do {
               document.write("Current Count : " + count + "<br />");
               count++;
            }
            
            while (count < 5);
            document.write ("Loop stopped!");
         //-->
      </script>      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Starting Loop
Current Count : 0 
Current Count : 1 
Current Count : 2 
Current Count : 3 
Current Count : 4
Loop Stopped!
Set the variable to different value and then try...

JavaScript - For Loop

The 'for' loop is the most compact form of looping. It includes the following three important parts −

  • The loop initialization where we initialize our counter to a starting value. The initialization statement is executed before the loop begins.

  • The test statement which will test if a given condition is true or not. If the condition is true, then the code given inside the loop will be executed, otherwise the control will come out of the loop.

  • The iteration statement where you can increase or decrease your counter.

You can put all the three parts in a single line separated by semicolons.

Flow Chart

The flow chart of a for loop in JavaScript would be as follows −

For Loop

Syntax

The syntax of for loop is JavaScript is as follows −

for (initialization; test condition; iteration statement) {
   Statement(s) to be executed if test condition is true
}

Example

Try the following example to learn how a for loop works in JavaScript.

Live Demo
<html>
   <body>      
      <script type = "text/javascript">
         <!--
            var count;
            document.write("Starting Loop" + "<br />");
         
            for(count = 0; count < 10; count++) {
               document.write("Current Count : " + count );
               document.write("<br />");
            }         
            document.write("Loop stopped!");
         //-->
      </script>      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Starting Loop
Current Count : 0
Current Count : 1
Current Count : 2
Current Count : 3
Current Count : 4
Current Count : 5
Current Count : 6
Current Count : 7
Current Count : 8
Current Count : 9
Loop stopped! 
Set the variable to different value and then try...

JavaScript for...in loop

The for...in loop is used to loop through an object's properties. As we have not discussed Objects yet, you may not feel comfortable with this loop. But once you understand how objects behave in JavaScript, you will find this loop very useful.

Syntax

The syntax of ‘for..in’ loop is −

for (variablename in object) {
   statement or block to execute
}

In each iteration, one property from object is assigned to variablename and this loop continues till all the properties of the object are exhausted.

Example

Try the following example to implement ‘for-in’ loop. It prints the web browser’s Navigator object.

Live Demo
<html>
   <body>      
      <script type = "text/javascript">
         <!--
            var aProperty;
            document.write("Navigator Object Properties<br /> ");        
            for (aProperty in navigator) {
               document.write(aProperty);
               document.write("<br />");
            }
            document.write ("Exiting from the loop!");
         //-->
      </script>      
      <p>Set the variable to different object and then try...</p>
   </body>
</html>

Output

Navigator Object Properties 
serviceWorker 
webkitPersistentStorage 
webkitTemporaryStorage 
geolocation 
doNotTrack 
onLine 
languages 
language 
userAgent 
product 
platform 
appVersion 
appName 
appCodeName 
hardwareConcurrency 
maxTouchPoints 
vendorSub 
vendor 
productSub 
cookieEnabled 
mimeTypes 
plugins 
javaEnabled 
getStorageUpdates 
getGamepads 
webkitGetUserMedia 
vibrate 
getBattery 
sendBeacon 
registerProtocolHandler 
unregisterProtocolHandler 
Exiting from the loop!
Set the variable to different object and then try...

JavaScript - Loop Control

JavaScript provides full control to handle loops and switch statements. There may be a situation when you need to come out of a loop without reaching its bottom. There may also be a situation when you want to skip a part of your code block and start the next iteration of the loop.

To handle all such situations, JavaScript provides break and continue statements. These statements are used to immediately come out of any loop or to start the next iteration of any loop respectively.

The break Statement

The break statement, which was briefly introduced with the switch statement, is used to exit a loop early, breaking out of the enclosing curly braces.

Flow Chart

The flow chart of a break statement would look as follows −

Break Statement

Example

The following example illustrates the use of a break statement with a while loop. Notice how the loop breaks out early once x reaches 5 and reaches to document.write (..) statement just below to the closing curly brace −

Live Demo
<html>
   <body>     
      <script type = "text/javascript">
         <!--
         var x = 1;
         document.write("Entering the loop<br /> ");
         
         while (x < 20) {
            if (x == 5) {
               break;   // breaks out of loop completely
            }
            x = x + 1;
            document.write( x + "<br />");
         }         
         document.write("Exiting the loop!<br /> ");
         //-->
      </script>
      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Entering the loop
2
3
4
5
Exiting the loop!
Set the variable to different value and then try...

We already have seen the usage of break statement inside a switch statement.

The continue Statement

The continue statement tells the interpreter to immediately start the next iteration of the loop and skip the remaining code block. When a continue statement is encountered, the program flow moves to the loop check expression immediately and if the condition remains true, then it starts the next iteration, otherwise the control comes out of the loop.

Example

This example illustrates the use of a continue statement with a while loop. Notice how the continue statement is used to skip printing when the index held in variable x reaches 5 −

Live Demo
<html>
   <body>      
      <script type = "text/javascript">
         <!--
            var x = 1;
            document.write("Entering the loop<br /> ");
         
            while (x < 10) {
               x = x + 1;
               
               if (x == 5) {
                  continue;   // skip rest of the loop body
               }
               document.write( x + "<br />");
            }         
            document.write("Exiting the loop!<br /> ");
         //-->
      </script>      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Entering the loop
2
3
4
6
7
8
9
10
Exiting the loop!
Set the variable to different value and then try...

Using Labels to Control the Flow

Starting from JavaScript 1.2, a label can be used with break and continue to control the flow more precisely. A label is simply an identifier followed by a colon (:) that is applied to a statement or a block of code. We will see two different examples to understand how to use labels with break and continue.

Note − Line breaks are not allowed between the ‘continue’ or ‘break’ statement and its label name. Also, there should not be any other statement in between a label name and associated loop.

Try the following two examples for a better understanding of Labels.

Example 1

The following example shows how to implement Label with a break statement.

Live Demo
<html>
   <body>      
      <script type = "text/javascript">
         <!--
            document.write("Entering the loop!<br /> ");
            outerloop:        // This is the label name         
            for (var i = 0; i < 5; i++) {
               document.write("Outerloop: " + i + "<br />");
               innerloop:
               for (var j = 0; j < 5; j++) {
                  if (j > 3 ) break ;           // Quit the innermost loop
                  if (i == 2) break innerloop;  // Do the same thing
                  if (i == 4) break outerloop;  // Quit the outer loop
                  document.write("Innerloop: " + j + " <br />");
               }
            }        
            document.write("Exiting the loop!<br /> ");
         //-->
      </script>      
   </body>
</html>

Output

Entering the loop!
Outerloop: 0
Innerloop: 0 
Innerloop: 1 
Innerloop: 2 
Innerloop: 3 
Outerloop: 1
Innerloop: 0 
Innerloop: 1 
Innerloop: 2 
Innerloop: 3 
Outerloop: 2
Outerloop: 3
Innerloop: 0 
Innerloop: 1 
Innerloop: 2 
Innerloop: 3 
Outerloop: 4
Exiting the loop!

Example 2

Live Demo
<html>
   <body>
   
      <script type = "text/javascript">
         <!--
         document.write("Entering the loop!<br /> ");
         outerloop:     // This is the label name
         
         for (var i = 0; i < 3; i++) {
            document.write("Outerloop: " + i + "<br />");
            for (var j = 0; j < 5; j++) {
               if (j == 3) {
                  continue outerloop;
               }
               document.write("Innerloop: " + j + "<br />");
            }
         }
         
         document.write("Exiting the loop!<br /> ");
         //-->
      </script>
      
   </body>
</html>

Output

Entering the loop!
Outerloop: 0
Innerloop: 0
Innerloop: 1
Innerloop: 2
Outerloop: 1
Innerloop: 0
Innerloop: 1
Innerloop: 2
Outerloop: 2
Innerloop: 0
Innerloop: 1
Innerloop: 2
Exiting the loop!

JavaScript - Functions

A function is a group of reusable code which can be called anywhere in your program. This eliminates the need of writing the same code again and again. It helps programmers in writing modular codes. Functions allow a programmer to divide a big program into a number of small and manageable functions.

Like any other advanced programming language, JavaScript also supports all the features necessary to write modular code using functions. You must have seen functions like alert() and write() in the earlier chapters. We were using these functions again and again, but they had been written in core JavaScript only once.

JavaScript allows us to write our own functions as well. This section explains how to write your own functions in JavaScript.

Function Definition

Before we use a function, we need to define it. The most common way to define a function in JavaScript is by using the function keyword, followed by a unique function name, a list of parameters (that might be empty), and a statement block surrounded by curly braces.

Syntax

The basic syntax is shown here.

<script type = "text/javascript">
   <!--
      function functionname(parameter-list) {
         statements
      }
   //-->
</script>

Example

Try the following example. It defines a function called sayHello that takes no parameters −

<script type = "text/javascript">
   <!--
      function sayHello() {
         alert("Hello there");
      }
   //-->
</script>

Calling a Function

To invoke a function somewhere later in the script, you would simply need to write the name of that function as shown in the following code.

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         function sayHello() {
            document.write ("Hello there!");
         }
      </script>
      
   </head>
   
   <body>
      <p>Click the following button to call the function</p>      
      <form>
         <input type = "button" onclick = "sayHello()" value = "Say Hello">
      </form>      
      <p>Use different text in write method and then try...</p>
   </body>
</html>

Output

Function Parameters

Till now, we have seen functions without parameters. But there is a facility to pass different parameters while calling a function. These passed parameters can be captured inside the function and any manipulation can be done over those parameters. A function can take multiple parameters separated by comma.

Example

Try the following example. We have modified our sayHello function here. Now it takes two parameters.

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         function sayHello(name, age) {
            document.write (name + " is " + age + " years old.");
         }
      </script>      
   </head>
   
   <body>
      <p>Click the following button to call the function</p>      
      <form>
         <input type = "button" onclick = "sayHello('Zara', 7)" value = "Say Hello">
      </form>      
      <p>Use different parameters inside the function and then try...</p>
   </body>
</html>

Output

The return Statement

A JavaScript function can have an optional return statement. This is required if you want to return a value from a function. This statement should be the last statement in a function.

For example, you can pass two numbers in a function and then you can expect the function to return their multiplication in your calling program.

Example

Try the following example. It defines a function that takes two parameters and concatenates them before returning the resultant in the calling program.

Live Demo
<html>
   <head>  
      <script type = "text/javascript">
         function concatenate(first, last) {
            var full;
            full = first + last;
            return full;
         }
         function secondFunction() {
            var result;
            result = concatenate('Zara', 'Ali');
            document.write (result );
         }
      </script>      
   </head>
   
   <body>
      <p>Click the following button to call the function</p>      
      <form>
         <input type = "button" onclick = "secondFunction()" value = "Call Function">
      </form>      
      <p>Use different parameters inside the function and then try...</p>  
  </body>
</html>

Output

There is a lot to learn about JavaScript functions, however we have covered the most important concepts in this tutorial.

  • JavaScript Nested Functions

  • JavaScript Function( ) Constructor

  • JavaScript Function Literals

JavaScript - Events

What is an Event ?

JavaScript's interaction with HTML is handled through events that occur when the user or the browser manipulates a page.

When the page loads, it is called an event. When the user clicks a button, that click too is an event. Other examples include events like pressing any key, closing a window, resizing a window, etc.

Developers can use these events to execute JavaScript coded responses, which cause buttons to close windows, messages to be displayed to users, data to be validated, and virtually any other type of response imaginable.

Events are a part of the Document Object Model (DOM) Level 3 and every HTML element contains a set of events which can trigger JavaScript Code.

Please go through this small tutorial for a better understanding HTML Event Reference. Here we will see a few examples to understand a relation between Event and JavaScript −

onclick Event Type

This is the most frequently used event type which occurs when a user clicks the left button of his mouse. You can put your validation, warning etc., against this event type.

Example

Try the following example.

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         <!--
            function sayHello() {
               alert("Hello World")
            }
         //-->
      </script>      
   </head>
   
   <body>
      <p>Click the following button and see result</p>      
      <form>
         <input type = "button" onclick = "sayHello()" value = "Say Hello" />
      </form>      
   </body>
</html>

Output

onsubmit Event Type

onsubmit is an event that occurs when you try to submit a form. You can put your form validation against this event type.

Example

The following example shows how to use onsubmit. Here we are calling a validate() function before submitting a form data to the webserver. If validate() function returns true, the form will be submitted, otherwise it will not submit the data.

Try the following example.

<html>
   <head>   
      <script type = "text/javascript">
         <!--
            function validation() {
               all validation goes here
               .........
               return either true or false
            }
         //-->
      </script>      
   </head>
   
   <body>   
      <form method = "POST" action = "t.cgi" onsubmit = "return validate()">
         .......
         <input type = "submit" value = "Submit" />
      </form>      
   </body>
</html>

onmouseover and onmouseout

These two event types will help you create nice effects with images or even with text as well. The onmouseover event triggers when you bring your mouse over any element and the onmouseout triggers when you move your mouse out from that element. Try the following example.

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         <!--
            function over() {
               document.write ("Mouse Over");
            }            
            function out() {
               document.write ("Mouse Out");
            }            
         //-->
      </script>      
   </head>
   
   <body>
      <p>Bring your mouse inside the division to see the result:</p>      
      <div onmouseover = "over()" onmouseout = "out()">
         <h2> This is inside the division </h2>
      </div>         
   </body>
</html>

Output

HTML 5 Standard Events

The standard HTML 5 events are listed here for your reference. Here script indicates a Javascript function to be executed against that event.

Attribute Value Description
Offline script Triggers when the document goes offline
Onabort script Triggers on an abort event
onafterprint script Triggers after the document is printed
onbeforeonload script Triggers before the document loads
onbeforeprint script Triggers before the document is printed
onblur script Triggers when the window loses focus
oncanplay script Triggers when media can start play, but might has to stop for buffering
oncanplaythrough script Triggers when media can be played to the end, without stopping for buffering
onchange script Triggers when an element changes
onclick script Triggers on a mouse click
oncontextmenu script Triggers when a context menu is triggered
ondblclick script Triggers on a mouse double-click
ondrag script Triggers when an element is dragged
ondragend script Triggers at the end of a drag operation
ondragenter script Triggers when an element has been dragged to a valid drop target
ondragleave script Triggers when an element is being dragged over a valid drop target
ondragover script Triggers at the start of a drag operation
ondragstart script Triggers at the start of a drag operation
ondrop script Triggers when dragged element is being dropped
ondurationchange script Triggers when the length of the media is changed
onemptied script Triggers when a media resource element suddenly becomes empty.
onended script Triggers when media has reach the end
onerror script Triggers when an error occur
onfocus script Triggers when the window gets focus
onformchange script Triggers when a form changes
onforminput script Triggers when a form gets user input
onhaschange script Triggers when the document has change
oninput script Triggers when an element gets user input
oninvalid script Triggers when an element is invalid
onkeydown script Triggers when a key is pressed
onkeypress script Triggers when a key is pressed and released
onkeyup script Triggers when a key is released
onload script Triggers when the document loads
onloadeddata script Triggers when media data is loaded
onloadedmetadata script Triggers when the duration and other media data of a media element is loaded
onloadstart script Triggers when the browser starts to load the media data
onmessage script Triggers when the message is triggered
onmousedown script Triggers when a mouse button is pressed
onmousemove script Triggers when the mouse pointer moves
onmouseout script Triggers when the mouse pointer moves out of an element
onmouseover script Triggers when the mouse pointer moves over an element
onmouseup script Triggers when a mouse button is released
onmousewheel script Triggers when the mouse wheel is being rotated
onoffline script Triggers when the document goes offline
onoine script Triggers when the document comes online
ononline script Triggers when the document comes online
onpagehide script Triggers when the window is hidden
onpageshow script Triggers when the window becomes visible
onpause script Triggers when media data is paused
onplay script Triggers when media data is going to start playing
onplaying script Triggers when media data has start playing
onpopstate script Triggers when the window's history changes
onprogress script Triggers when the browser is fetching the media data
onratechange script Triggers when the media data's playing rate has changed
onreadystatechange script Triggers when the ready-state changes
onredo script Triggers when the document performs a redo
onresize script Triggers when the window is resized
onscroll script Triggers when an element's scrollbar is being scrolled
onseeked script Triggers when a media element's seeking attribute is no longer true, and the seeking has ended
onseeking script Triggers when a media element's seeking attribute is true, and the seeking has begun
onselect script Triggers when an element is selected
onstalled script Triggers when there is an error in fetching media data
onstorage script Triggers when a document loads
onsubmit script Triggers when a form is submitted
onsuspend script Triggers when the browser has been fetching media data, but stopped before the entire media file was fetched
ontimeupdate script Triggers when media changes its playing position
onundo script Triggers when a document performs an undo
onunload script Triggers when the user leaves the document
onvolumechange script Triggers when media changes the volume, also when volume is set to "mute"
onwaiting script Triggers when media has stopped playing, but is expected to resume

JavaScript and Cookies

What are Cookies ?

Web Browsers and Servers use HTTP protocol to communicate and HTTP is a stateless protocol. But for a commercial website, it is required to maintain session information among different pages. For example, one user registration ends after completing many pages. But how to maintain users' session information across all the web pages.

In many situations, using cookies is the most efficient method of remembering and tracking preferences, purchases, commissions, and other information required for better visitor experience or site statistics.

How It Works ?

Your server sends some data to the visitor's browser in the form of a cookie. The browser may accept the cookie. If it does, it is stored as a plain text record on the visitor's hard drive. Now, when the visitor arrives at another page on your site, the browser sends the same cookie to the server for retrieval. Once retrieved, your server knows/remembers what was stored earlier.

Cookies are a plain text data record of 5 variable-length fields −

  • Expires − The date the cookie will expire. If this is blank, the cookie will expire when the visitor quits the browser.

  • Domain − The domain name of your site.

  • Path − The path to the directory or web page that set the cookie. This may be blank if you want to retrieve the cookie from any directory or page.

  • Secure − If this field contains the word "secure", then the cookie may only be retrieved with a secure server. If this field is blank, no such restriction exists.

  • Name=Value − Cookies are set and retrieved in the form of key-value pairs

Cookies were originally designed for CGI programming. The data contained in a cookie is automatically transmitted between the web browser and the web server, so CGI scripts on the server can read and write cookie values that are stored on the client.

JavaScript can also manipulate cookies using the cookie property of the Document object. JavaScript can read, create, modify, and delete the cookies that apply to the current web page.

Storing Cookies

The simplest way to create a cookie is to assign a string value to the document.cookie object, which looks like this.

document.cookie = "key1 = value1;key2 = value2;expires = date";

Here the expires attribute is optional. If you provide this attribute with a valid date or time, then the cookie will expire on a given date or time and thereafter, the cookies' value will not be accessible.

Note − Cookie values may not include semicolons, commas, or whitespace. For this reason, you may want to use the JavaScript escape() function to encode the value before storing it in the cookie. If you do this, you will also have to use the corresponding unescape() function when you read the cookie value.

Example

Try the following. It sets a customer name in an input cookie.

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         <!--
            function WriteCookie() {
               if( document.myform.customer.value == "" ) {
                  alert("Enter some value!");
                  return;
               }
               cookievalue = escape(document.myform.customer.value) + ";";
               document.cookie = "name=" + cookievalue;
               document.write ("Setting Cookies : " + "name=" + cookievalue );
            }
         //-->
      </script>      
   </head>
   
   <body>      
      <form name = "myform" action = "">
         Enter name: <input type = "text" name = "customer"/>
         <input type = "button" value = "Set Cookie" onclick = "WriteCookie();"/>
      </form>   
   </body>
</html>

Output

Now your machine has a cookie called name. You can set multiple cookies using multiple key = value pairs separated by comma.

Reading Cookies

Reading a cookie is just as simple as writing one, because the value of the document.cookie object is the cookie. So you can use this string whenever you want to access the cookie. The document.cookie string will keep a list of name=value pairs separated by semicolons, where name is the name of a cookie and value is its string value.

You can use strings' split() function to break a string into key and values as follows −

Example

Try the following example to get all the cookies.

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         <!--
            function ReadCookie() {
               var allcookies = document.cookie;
               document.write ("All Cookies : " + allcookies );
               
               // Get all the cookies pairs in an array
               cookiearray = allcookies.split(';');
               
               // Now take key value pair out of this array
               for(var i=0; i<cookiearray.length; i++) {
                  name = cookiearray[i].split('=')[0];
                  value = cookiearray[i].split('=')[1];
                  document.write ("Key is : " + name + " and Value is : " + value);
               }
            }
         //-->
      </script>      
   </head>
   
   <body>     
      <form name = "myform" action = "">
         <p> click the following button and see the result:</p>
         <input type = "button" value = "Get Cookie" onclick = "ReadCookie()"/>
      </form>      
   </body>
</html>

Note − Here length is a method of Array class which returns the length of an array. We will discuss Arrays in a separate chapter. By that time, please try to digest it.

Note − There may be some other cookies already set on your machine. The above code will display all the cookies set on your machine.

Setting Cookies Expiry Date

You can extend the life of a cookie beyond the current browser session by setting an expiration date and saving the expiry date within the cookie. This can be done by setting the ‘expires’ attribute to a date and time.

Example

Try the following example. It illustrates how to extend the expiry date of a cookie by 1 Month.

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         <!--
            function WriteCookie() {
               var now = new Date();
               now.setMonth( now.getMonth() + 1 );
               cookievalue = escape(document.myform.customer.value) + ";"
               
               document.cookie = "name=" + cookievalue;
               document.cookie = "expires=" + now.toUTCString() + ";"
               document.write ("Setting Cookies : " + "name=" + cookievalue );
            }
         //-->
      </script>      
   </head>
   
   <body>
      <form name = "myform" action = "">
         Enter name: <input type = "text" name = "customer"/>
         <input type = "button" value = "Set Cookie" onclick = "WriteCookie()"/>
      </form>      
   </body>
</html>

Output

Deleting a Cookie

Sometimes you will want to delete a cookie so that subsequent attempts to read the cookie return nothing. To do this, you just need to set the expiry date to a time in the past.

Example

Try the following example. It illustrates how to delete a cookie by setting its expiry date to one month behind the current date.

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         <!--
            function WriteCookie() {
               var now = new Date();
               now.setMonth( now.getMonth() - 1 );
               cookievalue = escape(document.myform.customer.value) + ";"
               
               document.cookie = "name=" + cookievalue;
               document.cookie = "expires=" + now.toUTCString() + ";"
               document.write("Setting Cookies : " + "name=" + cookievalue );
            }
          //-->
      </script>      
   </head>
   
   <body>
      <form name = "myform" action = "">
         Enter name: <input type = "text" name = "customer"/>
         <input type = "button" value = "Set Cookie" onclick = "WriteCookie()"/>
      </form>      
   </body>
</html>

Output

JavaScript - Page Redirection

What is Page Redirection ?

You might have encountered a situation where you clicked a URL to reach a page X but internally you were directed to another page Y. It happens due to page redirection. This concept is different from JavaScript Page Refresh.

There could be various reasons why you would like to redirect a user from the original page. We are listing down a few of the reasons −

  • You did not like the name of your domain and you are moving to a new one. In such a scenario, you may want to direct all your visitors to the new site. Here you can maintain your old domain but put a single page with a page redirection such that all your old domain visitors can come to your new domain.

  • You have built-up various pages based on browser versions or their names or may be based on different countries, then instead of using your server-side page redirection, you can use client-side page redirection to land your users on the appropriate page.

  • The Search Engines may have already indexed your pages. But while moving to another domain, you would not like to lose your visitors coming through search engines. So you can use client-side page redirection. But keep in mind this should not be done to fool the search engine, it could lead your site to get banned.

How Page Re-direction Works ?

The implementations of Page-Redirection are as follows.

Example 1

It is quite simple to do a page redirect using JavaScript at client side. To redirect your site visitors to a new page, you just need to add a line in your head section as follows.

Live Demo
<html>
   <head>
      <script type = "text/javascript">
         <!--
            function Redirect() {
               window.location = "https://www.tutorialspoint.com";
            }
         //-->
      </script>
   </head>
   
   <body>
      <p>Click the following button, you will be redirected to home page.</p>
      
      <form>
         <input type = "button" value = "Redirect Me" onclick = "Redirect();" />
      </form>
      
   </body>
</html>

Output

Example 2

You can show an appropriate message to your site visitors before redirecting them to a new page. This would need a bit time delay to load a new page. The following example shows how to implement the same. Here setTimeout() is a built-in JavaScript function which can be used to execute another function after a given time interval.

Live Demo
<html>
   <head>
      <script type = "text/javascript">
         <!--
            function Redirect() {
               window.location = "https://www.yoursite.com";
            }            
            document.write("You will be redirected to main page in 10 sec.");
            setTimeout('Redirect()', 10000);
         //-->
      </script>
   </head>
   
   <body>
   </body>
</html>

Output

You will be redirected to yoursite.com main page in 10 seconds!

Example 3

The following example shows how to redirect your site visitors onto a different page based on their browsers.

<html>
   <head>     
      <script type = "text/javascript">
         <!--
            var browsername = navigator.appName;
            if( browsername == "Netscape" ) {
               window.location = "http://www.location.com/ns.htm";
            } else if ( browsername =="Microsoft Internet Explorer") {
               window.location = "http://www.location.com/ie.htm";
            } else {
               window.location = "http://www.location.com/other.htm";
            }
         //-->
      </script>      
   </head>
   
   <body>
   </body>
</html>

JavaScript - Dialog Boxes

JavaScript supports three important types of dialog boxes. These dialog boxes can be used to raise and alert, or to get confirmation on any input or to have a kind of input from the users. Here we will discuss each dialog box one by one.

Alert Dialog Box

An alert dialog box is mostly used to give a warning message to the users. For example, if one input field requires to enter some text but the user does not provide any input, then as a part of validation, you can use an alert box to give a warning message.

Nonetheless, an alert box can still be used for friendlier messages. Alert box gives only one button "OK" to select and proceed.

Example

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         <!--
            function Warn() {
               alert ("This is a warning message!");
               document.write ("This is a warning message!");
            }
         //-->
      </script>     
   </head>
   
   <body>
      <p>Click the following button to see the result: </p>      
      <form>
         <input type = "button" value = "Click Me" onclick = "Warn();" />
      </form>     
   </body>
</html>

Output

Confirmation Dialog Box

A confirmation dialog box is mostly used to take user's consent on any option. It displays a dialog box with two buttons: OK and Cancel.

If the user clicks on the OK button, the window method confirm() will return true. If the user clicks on the Cancel button, then confirm() returns false. You can use a confirmation dialog box as follows.

Example

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         <!--
            function getConfirmation() {
               var retVal = confirm("Do you want to continue ?");
               if( retVal == true ) {
                  document.write ("User wants to continue!");
                  return true;
               } else {
                  document.write ("User does not want to continue!");
                  return false;
               }
            }
         //-->
      </script>     
   </head>
   
   <body>
      <p>Click the following button to see the result: </p>      
      <form>
         <input type = "button" value = "Click Me" onclick = "getConfirmation();" />
      </form>      
   </body>
</html>

Output

Prompt Dialog Box

The prompt dialog box is very useful when you want to pop-up a text box to get user input. Thus, it enables you to interact with the user. The user needs to fill in the field and then click OK.

This dialog box is displayed using a method called prompt() which takes two parameters: (i) a label which you want to display in the text box and (ii) a default string to display in the text box.

This dialog box has two buttons: OK and Cancel. If the user clicks the OK button, the window method prompt() will return the entered value from the text box. If the user clicks the Cancel button, the window method prompt() returns null.

Example

The following example shows how to use a prompt dialog box −

Live Demo
<html>
   <head>     
      <script type = "text/javascript">
         <!--
            function getValue() {
               var retVal = prompt("Enter your name : ", "your name here");
               document.write("You have entered : " + retVal);
            }
         //-->
      </script>      
   </head>
   
   <body>
      <p>Click the following button to see the result: </p>      
      <form>
         <input type = "button" value = "Click Me" onclick = "getValue();" />
      </form>      
   </body>
</html>

Output

JavaScript - Void Keyword

void is an important keyword in JavaScript which can be used as a unary operator that appears before its single operand, which may be of any type. This operator specifies an expression to be evaluated without returning a value.

Syntax

The syntax of void can be either of the following two −

<head>
   <script type = "text/javascript">
      <!--
         void func()
         javascript:void func()
         or:
         void(func())
         javascript:void(func())
      //-->
   </script>
</head>

Example 1

The most common use of this operator is in a client-side javascript: URL, where it allows you to evaluate an expression for its side-effects without the browser displaying the value of the evaluated expression.

Here the expression alert ('Warning!!!') is evaluated but it is not loaded back into the current document −

Live Demo
<html>
   <head>      
      <script type = "text/javascript">
         <!--
         //-->
      </script>   
   </head>
   
   <body>   
      <p>Click the following, This won't react at all...</p>
      <a href = "javascript:void(alert('Warning!!!'))">Click me!</a>     
   </body>
</html>

Output

Example 2

Take a look at the following example. The following link does nothing because the expression "0" has no effect in JavaScript. Here the expression "0" is evaluated, but it is not loaded back into the current document.

Live Demo
<html>
   <head>   
      <script type = "text/javascript">
         <!--
         //-->
      </script>      
   </head>
   
   <body>   
      <p>Click the following, This won't react at all...</p>
      <a href = "javascript:void(0)">Click me!</a>      
   </body>
</html>

Output

Example 3

Another use of void is to purposely generate the undefined value as follows.

Live Demo
<html>
   <head>      
      <script type = "text/javascript">
         <!--
            function getValue() {
               var a,b,c;
               
               a = void ( b = 5, c = 7 );
               document.write('a = ' + a + ' b = ' + b +' c = ' + c );
            }
         //-->
      </script>      
   </head>
   
   <body>
      <p>Click the following to see the result:</p>
      <form>
         <input type = "button" value = "Click Me" onclick = "getValue();" />
      </form>     
   </body>
</html>

Output

JavaScript - Page Printing

Many times you would like to place a button on your webpage to print the content of that web page via an actual printer. JavaScript helps you to implement this functionality using the print function of window object.

The JavaScript print function window.print() prints the current web page when executed. You can call this function directly using the onclick event as shown in the following example.

Example

Try the following example.

Live Demo
<html>
   <head>      
      <script type = "text/javascript">
         <!--
         //-->
      </script>
   </head>
   
   <body>      
      <form>
         <input type = "button" value = "Print" onclick = "window.print()" />
      </form>   
   </body>
<html>

Output

Although it serves the purpose of getting a printout, it is not a recommended way. A printer friendly page is really just a page with text, no images, graphics, or advertising.

You can make a page printer friendly in the following ways −

  • Make a copy of the page and leave out unwanted text and graphics, then link to that printer friendly page from the original. Check Example.

  • If you do not want to keep an extra copy of a page, then you can mark your printable text using proper comments like <!-- PRINT STARTS HERE -->..... <!-- PRINT ENDS HERE --> and then you can use PERL or any other script in the background to purge printable text and display for final printing. We at yoursite use this method to provide print facility to our site visitors.

How to Print a Page?

If you don’t find the above facilities on a web page, then you can use the browser's standard toolbar to get print the web page. Follow the link as follows.

File →  Print → Click OK  button.

JavaScript - Objects Overview

JavaScript is an Object Oriented Programming (OOP) language. A programming language can be called object-oriented if it provides four basic capabilities to developers −

  • Encapsulation − the capability to store related information, whether data or methods, together in an object.

  • Aggregation − the capability to store one object inside another object.

  • Inheritance − the capability of a class to rely upon another class (or number of classes) for some of its properties and methods.

  • Polymorphism − the capability to write one function or method that works in a variety of different ways.

Objects are composed of attributes. If an attribute contains a function, it is considered to be a method of the object, otherwise the attribute is considered a property.

Object Properties

Object properties can be any of the three primitive data types, or any of the abstract data types, such as another object. Object properties are usually variables that are used internally in the object's methods, but can also be globally visible variables that are used throughout the page.

The syntax for adding a property to an object is −

objectName.objectProperty = propertyValue;

For example − The following code gets the document title using the "title" property of the document object.

var str = document.title;

Object Methods

Methods are the functions that let the object do something or let something be done to it. There is a small difference between a function and a method – at a function is a standalone unit of statements and a method is attached to an object and can be referenced by the this keyword.

Methods are useful for everything from displaying the contents of the object to the screen to performing complex mathematical operations on a group of local properties and parameters.

For example − Following is a simple example to show how to use the write() method of document object to write any content on the document.

document.write("This is test");

User-Defined Objects

All user-defined objects and built-in objects are descendants of an object called Object.

The new Operator

The new operator is used to create an instance of an object. To create an object, the new operator is followed by the constructor method.

In the following example, the constructor methods are Object(), Array(), and Date(). These constructors are built-in JavaScript functions.

var employee = new Object();
var books = new Array("C++", "Perl", "Java");
var day = new Date("August 15, 1947");

The Object() Constructor

A constructor is a function that creates and initializes an object. JavaScript provides a special constructor function called Object() to build the object. The return value of the Object() constructor is assigned to a variable.

The variable contains a reference to the new object. The properties assigned to the object are not variables and are not defined with the var keyword.

Example 1

Try the following example; it demonstrates how to create an Object.

Live Demo
<html>
   <head>
      <title>User-defined objects</title>     
      <script type = "text/javascript">
         var book = new Object();   // Create the object
         book.subject = "Perl";     // Assign properties to the object
         book.author  = "Mohtashim";
      </script>      
   </head>
   
   <body>  
      <script type = "text/javascript">
         document.write("Book name is : " + book.subject + "<br>");
         document.write("Book author is : " + book.author + "<br>");
      </script>   
   </body>
</html>

Output

Book name is : Perl 
Book author is : Mohtashim

Example 2

This example demonstrates how to create an object with a User-Defined Function. Here this keyword is used to refer to the object that has been passed to a function.

Live Demo
<html>
   <head>   
   <title>User-defined objects</title>
      <script type = "text/javascript">
         function book(title, author) {
            this.title = title; 
            this.author  = author;
         }
      </script>      
   </head>
   
   <body>   
      <script type = "text/javascript">
         var myBook = new book("Perl", "Mohtashim");
         document.write("Book title is : " + myBook.title + "<br>");
         document.write("Book author is : " + myBook.author + "<br>");
      </script>      
   </body>
</html>

Output

Book title is : Perl 
Book author is : Mohtashim

Defining Methods for an Object

The previous examples demonstrate how the constructor creates the object and assigns properties. But we need to complete the definition of an object by assigning methods to it.

Example

Try the following example; it shows how to add a function along with an object.

Live Demo
<html>
   
   <head>
   <title>User-defined objects</title>
      <script type = "text/javascript">
         // Define a function which will work as a method
         function addPrice(amount) {
            this.price = amount; 
         }
         
         function book(title, author) {
            this.title = title;
            this.author  = author;
            this.addPrice = addPrice;  // Assign that method as property.
         }
      </script>      
   </head>
   
   <body>   
      <script type = "text/javascript">
         var myBook = new book("Perl", "Mohtashim");
         myBook.addPrice(100);
         
         document.write("Book title is : " + myBook.title + "<br>");
         document.write("Book author is : " + myBook.author + "<br>");
         document.write("Book price is : " + myBook.price + "<br>");
      </script>      
   </body>
</html>

Output

Book title is : Perl 
Book author is : Mohtashim 
Book price is : 100

The 'with' Keyword

The ‘with’ keyword is used as a kind of shorthand for referencing an object's properties or methods.

The object specified as an argument to with becomes the default object for the duration of the block that follows. The properties and methods for the object can be used without naming the object.

Syntax

The syntax for with object is as follows −

with (object) {
   properties used without the object name and dot
}

Example

Try the following example.

Live Demo
<html>
   <head>
   <title>User-defined objects</title>   
      <script type = "text/javascript">
         // Define a function which will work as a method
         function addPrice(amount) {
            with(this) {
               price = amount;
            }
         }
         function book(title, author) {
            this.title = title;
            this.author = author;
            this.price = 0;
            this.addPrice = addPrice;  // Assign that method as property.
         }
      </script>      
   </head>
   
   <body>   
      <script type = "text/javascript">
         var myBook = new book("Perl", "Mohtashim");
         myBook.addPrice(100);
         
         document.write("Book title is : " + myBook.title + "<br>");
         document.write("Book author is : " + myBook.author + "<br>");
         document.write("Book price is : " + myBook.price + "<br>");
      </script>      
   </body>
</html>

Output

Book title is : Perl 
Book author is : Mohtashim 
Book price is : 100

JavaScript Native Objects

JavaScript has several built-in or native objects. These objects are accessible anywhere in your program and will work the same way in any browser running in any operating system.

Here is the list of all important JavaScript Native Objects −

  • JavaScript Number Object

  • JavaScript Boolean Object

  • JavaScript String Object

  • JavaScript Array Object

  • JavaScript Date Object

  • JavaScript Math Object

  • JavaScript RegExp Object

JavaScript - The Number Object

The Number object represents numerical date, either integers or floating-point numbers. In general, you do not need to worry about Number objects because the browser automatically converts number literals to instances of the number class.

Syntax

The syntax for creating a number object is as follows −

var val = new Number(number);

In the place of number, if you provide any non-number argument, then the argument cannot be converted into a number, it returns NaN (Not-a-Number).

Number Properties

Here is a list of each property and their description.

Sr.No. Property & Description
1 MAX_VALUE

The largest possible value a number in JavaScript can have 1.7976931348623157E+308

2 MIN_VALUE

The smallest possible value a number in JavaScript can have 5E-324

3 NaN

Equal to a value that is not a number.

4 NEGATIVE_INFINITY

A value that is less than MIN_VALUE.

5 POSITIVE_INFINITY

A value that is greater than MAX_VALUE

6 prototype

A static property of the Number object. Use the prototype property to assign new properties and methods to the Number object in the current document

7 constructor

Returns the function that created this object's instance. By default this is the Number object.

In the following sections, we will take a few examples to demonstrate the properties of Number.

Number Methods

The Number object contains only the default methods that are a part of every object's definition.

Sr.No. Method & Description
1 toExponential()

Forces a number to display in exponential notation, even if the number is in the range in which JavaScript normally uses standard notation.

2 toFixed()

Formats a number with a specific number of digits to the right of the decimal.

3 toLocaleString()

Returns a string value version of the current number in a format that may vary according to a browser's local settings.

4 toPrecision()

Defines how many total digits (including digits to the left and right of the decimal) to display of a number.

5 toString()

Returns the string representation of the number's value.

6 valueOf()

Returns the number's value.

In the following sections, we will have a few examples to explain the methods of Number.

JavaScript - The Boolean Object

The Boolean object represents two values, either "true" or "false". If value parameter is omitted or is 0, -0, null, false, NaN, undefined, or the empty string (""), the object has an initial value of false.

Syntax

Use the following syntax to create a boolean object.

var val = new Boolean(value);

Boolean Properties

Here is a list of the properties of Boolean object −

Sr.No. Property & Description
1 constructor

Returns a reference to the Boolean function that created the object.

2 prototype

The prototype property allows you to add properties and methods to an object.

In the following sections, we will have a few examples to illustrate the properties of Boolean object.

Boolean Methods

Here is a list of the methods of Boolean object and their description.

Sr.No. Method & Description
1 toSource()

Returns a string containing the source of the Boolean object; you can use this string to create an equivalent object.

2 toString()

Returns a string of either "true" or "false" depending upon the value of the object.

3 valueOf()

Returns the primitive value of the Boolean object.

In the following sections, we will have a few examples to demonstrate the usage of the Boolean methods.

JavaScript - The Strings Object

The String object lets you work with a series of characters; it wraps Javascript's string primitive data type with a number of helper methods.

As JavaScript automatically converts between string primitives and String objects, you can call any of the helper methods of the String object on a string primitive.

Syntax

Use the following syntax to create a String object −

var val = new String(string);

The String parameter is a series of characters that has been properly encoded.

String Properties

Here is a list of the properties of String object and their description.

Sr.No. Property & Description
1 constructor

Returns a reference to the String function that created the object.

2 length

Returns the length of the string.

3 prototype

The prototype property allows you to add properties and methods to an object.

In the following sections, we will have a few examples to demonstrate the usage of String properties.

String Methods

Here is a list of the methods available in String object along with their description.

Sr.No. Method & Description
1 charAt()

Returns the character at the specified index.

2 charCodeAt()

Returns a number indicating the Unicode value of the character at the given index.

3 concat()

Combines the text of two strings and returns a new string.

4 indexOf()

Returns the index within the calling String object of the first occurrence of the specified value, or -1 if not found.

5 lastIndexOf()

Returns the index within the calling String object of the last occurrence of the specified value, or -1 if not found.

6 localeCompare()

Returns a number indicating whether a reference string comes before or after or is the same as the given string in sort order.

7 match()

Used to match a regular expression against a string.

8 replace()

Used to find a match between a regular expression and a string, and to replace the matched substring with a new substring.

9 search()

Executes the search for a match between a regular expression and a specified string.

10 slice()

Extracts a section of a string and returns a new string.

11 split()

Splits a String object into an array of strings by separating the string into substrings.

12 substr()

Returns the characters in a string beginning at the specified location through the specified number of characters.

13 substring()

Returns the characters in a string between two indexes into the string.

14 toLocaleLowerCase()

The characters within a string are converted to lower case while respecting the current locale.

15 toLocaleUpperCase()

The characters within a string are converted to upper case while respecting the current locale.

16 toLowerCase()

Returns the calling string value converted to lower case.

17 toString()

Returns a string representing the specified object.

18 toUpperCase()

Returns the calling string value converted to uppercase.

19 valueOf()

Returns the primitive value of the specified object.

String HTML Wrappers

Here is a list of the methods that return a copy of the string wrapped inside an appropriate HTML tag.

Sr.No. Method & Description
1 anchor()

Creates an HTML anchor that is used as a hypertext target.

2 big()

Creates a string to be displayed in a big font as if it were in a <big> tag.

3 blink()

Creates a string to blink as if it were in a <blink> tag.

4 bold()

Creates a string to be displayed as bold as if it were in a <b> tag.

5 fixed()

Causes a string to be displayed in fixed-pitch font as if it were in a <tt> tag

6 fontcolor()

Causes a string to be displayed in the specified color as if it were in a <font color="color"> tag.

7 fontsize()

Causes a string to be displayed in the specified font size as if it were in a <font size="size"> tag.

8 italics()

Causes a string to be italic, as if it were in an <i> tag.

9 link()

Creates an HTML hypertext link that requests another URL.

10 small()

Causes a string to be displayed in a small font, as if it were in a <small> tag.

11 strike()

Causes a string to be displayed as struck-out text, as if it were in a <strike> tag.

12 sub()

Causes a string to be displayed as a subscript, as if it were in a <sub> tag

13 sup()

Causes a string to be displayed as a superscript, as if it were in a <sup> tag

In the following sections, we will have a few examples to demonstrate the usage of String methods.

JavaScript - The Arrays Object

The Array object lets you store multiple values in a single variable. It stores a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Syntax

Use the following syntax to create an Array object −

var fruits = new Array( "apple", "orange", "mango" );

The Array parameter is a list of strings or integers. When you specify a single numeric parameter with the Array constructor, you specify the initial length of the array. The maximum length allowed for an array is 4,294,967,295.

You can create array by simply assigning values as follows −

var fruits = [ "apple", "orange", "mango" ];

You will use ordinal numbers to access and to set values inside an array as follows.

fruits[0] is the first element
fruits[1] is the second element
fruits[2] is the third element

Array Properties

Here is a list of the properties of the Array object along with their description.

Sr.No. Property & Description
1 constructor

Returns a reference to the array function that created the object.

2

index

The property represents the zero-based index of the match in the string

3

input

This property is only present in arrays created by regular expression matches.

4 length

Reflects the number of elements in an array.

5 prototype

The prototype property allows you to add properties and methods to an object.

In the following sections, we will have a few examples to illustrate the usage of Array properties.

Array Methods

Here is a list of the methods of the Array object along with their description.

Sr.No. Method & Description
1 concat()

Returns a new array comprised of this array joined with other array(s) and/or value(s).

2 every()

Returns true if every element in this array satisfies the provided testing function.

3 filter()

Creates a new array with all of the elements of this array for which the provided filtering function returns true.

4 forEach()

Calls a function for each element in the array.

5 indexOf()

Returns the first (least) index of an element within the array equal to the specified value, or -1 if none is found.

6 join()

Joins all elements of an array into a string.

7 lastIndexOf()

Returns the last (greatest) index of an element within the array equal to the specified value, or -1 if none is found.

8 map()

Creates a new array with the results of calling a provided function on every element in this array.

9 pop()

Removes the last element from an array and returns that element.

10 push()

Adds one or more elements to the end of an array and returns the new length of the array.

11 reduce()

Apply a function simultaneously against two values of the array (from left-to-right) as to reduce it to a single value.

12 reduceRight()

Apply a function simultaneously against two values of the array (from right-to-left) as to reduce it to a single value.

13 reverse()

Reverses the order of the elements of an array -- the first becomes the last, and the last becomes the first.

14 shift()

Removes the first element from an array and returns that element.

15 slice()

Extracts a section of an array and returns a new array.

16 some()

Returns true if at least one element in this array satisfies the provided testing function.

17 toSource()

Represents the source code of an object

18 sort()

Sorts the elements of an array

19 splice()

Adds and/or removes elements from an array.

20 toString()

Returns a string representing the array and its elements.

21 unshift()

Adds one or more elements to the front of an array and returns the new length of the array.

In the following sections, we will have a few examples to demonstrate the usage of Array methods.

JavaScript - The Date Object

The Date object is a datatype built into the JavaScript language. Date objects are created with the new Date( ) as shown below.

Once a Date object is created, a number of methods allow you to operate on it. Most methods simply allow you to get and set the year, month, day, hour, minute, second, and millisecond fields of the object, using either local time or UTC (universal, or GMT) time.

The ECMAScript standard requires the Date object to be able to represent any date and time, to millisecond precision, within 100 million days before or after 1/1/1970. This is a range of plus or minus 273,785 years, so JavaScript can represent date and time till the year 275755.

Syntax

You can use any of the following syntaxes to create a Date object using Date() constructor.

new Date( )
new Date(milliseconds)
new Date(datestring)
new Date(year,month,date[,hour,minute,second,millisecond ])

Note − Parameters in the brackets are always optional.

Here is a description of the parameters −

  • No Argument − With no arguments, the Date() constructor creates a Date object set to the current date and time.

  • milliseconds − When one numeric argument is passed, it is taken as the internal numeric representation of the date in milliseconds, as returned by the getTime() method. For example, passing the argument 5000 creates a date that represents five seconds past midnight on 1/1/70.

  • datestring − When one string argument is passed, it is a string representation of a date, in the format accepted by the Date.parse() method.

  • 7 agruments − To use the last form of the constructor shown above. Here is a description of each argument −

    • year − Integer value representing the year. For compatibility (in order to avoid the Y2K problem), you should always specify the year in full; use 1998, rather than 98.

    • month − Integer value representing the month, beginning with 0 for January to 11 for December.

    • date − Integer value representing the day of the month.

    • hour − Integer value representing the hour of the day (24-hour scale).

    • minute − Integer value representing the minute segment of a time reading.

    • second − Integer value representing the second segment of a time reading.

    • millisecond − Integer value representing the millisecond segment of a time reading.

Date Properties

Here is a list of the properties of the Date object along with their description.

Sr.No. Property & Description
1 constructor

Specifies the function that creates an object's prototype.

2 prototype

The prototype property allows you to add properties and methods to an object

In the following sections, we will have a few examples to demonstrate the usage of different Date properties.

Date Methods

Here is a list of the methods used with Date and their description.

Sr.No. Method & Description
1 Date()

Returns today's date and time

2 getDate()

Returns the day of the month for the specified date according to local time.

3 getDay()

Returns the day of the week for the specified date according to local time.

4 getFullYear()

Returns the year of the specified date according to local time.

5 getHours()

Returns the hour in the specified date according to local time.

6 getMilliseconds()

Returns the milliseconds in the specified date according to local time.

7 getMinutes()

Returns the minutes in the specified date according to local time.

8 getMonth()

Returns the month in the specified date according to local time.

9 getSeconds()

Returns the seconds in the specified date according to local time.

10 getTime()

Returns the numeric value of the specified date as the number of milliseconds since January 1, 1970, 00:00:00 UTC.

11 getTimezoneOffset()

Returns the time-zone offset in minutes for the current locale.

12 getUTCDate()

Returns the day (date) of the month in the specified date according to universal time.

13 getUTCDay()

Returns the day of the week in the specified date according to universal time.

14 getUTCFullYear()

Returns the year in the specified date according to universal time.

15 getUTCHours()

Returns the hours in the specified date according to universal time.

16 getUTCMilliseconds()

Returns the milliseconds in the specified date according to universal time.

17 getUTCMinutes()

Returns the minutes in the specified date according to universal time.

18 getUTCMonth()

Returns the month in the specified date according to universal time.

19 getUTCSeconds()

Returns the seconds in the specified date according to universal time.

20 getYear()

Deprecated - Returns the year in the specified date according to local time. Use getFullYear instead.

21 setDate()

Sets the day of the month for a specified date according to local time.

22 setFullYear()

Sets the full year for a specified date according to local time.

23 setHours()

Sets the hours for a specified date according to local time.

24 setMilliseconds()

Sets the milliseconds for a specified date according to local time.

25 setMinutes()

Sets the minutes for a specified date according to local time.

26 setMonth()

Sets the month for a specified date according to local time.

27 setSeconds()

Sets the seconds for a specified date according to local time.

28 setTime()

Sets the Date object to the time represented by a number of milliseconds since January 1, 1970, 00:00:00 UTC.

29 setUTCDate()

Sets the day of the month for a specified date according to universal time.

30 setUTCFullYear()

Sets the full year for a specified date according to universal time.

31 setUTCHours()

Sets the hour for a specified date according to universal time.

32 setUTCMilliseconds()

Sets the milliseconds for a specified date according to universal time.

33 setUTCMinutes()

Sets the minutes for a specified date according to universal time.

34 setUTCMonth()

Sets the month for a specified date according to universal time.

35 setUTCSeconds()

Sets the seconds for a specified date according to universal time.

36 setYear()

Deprecated - Sets the year for a specified date according to local time. Use setFullYear instead.

37 toDateString()

Returns the "date" portion of the Date as a human-readable string.

38 toGMTString()

Deprecated - Converts a date to a string, using the Internet GMT conventions. Use toUTCString instead.

39 toLocaleDateString()

Returns the "date" portion of the Date as a string, using the current locale's conventions.

40 toLocaleFormat()

Converts a date to a string, using a format string.

41 toLocaleString()

Converts a date to a string, using the current locale's conventions.

42 toLocaleTimeString()

Returns the "time" portion of the Date as a string, using the current locale's conventions.

43 toSource()

Returns a string representing the source for an equivalent Date object; you can use this value to create a new object.

44 toString()

Returns a string representing the specified Date object.

45 toTimeString()

Returns the "time" portion of the Date as a human-readable string.

46 toUTCString()

Converts a date to a string, using the universal time convention.

47 valueOf()

Returns the primitive value of a Date object.

Converts a date to a string, using the universal time convention.

Date Static Methods

In addition to the many instance methods listed previously, the Date object also defines two static methods. These methods are invoked through the Date() constructor itself.

Sr.No. Method & Description
1 Date.parse( )

Parses a string representation of a date and time and returns the internal millisecond representation of that date.

2 Date.UTC( )

Returns the millisecond representation of the specified UTC date and time.

In the following sections, we will have a few examples to demonstrate the usages of Date Static methods.

JavaScript - The Math Object

The math object provides you properties and methods for mathematical constants and functions. Unlike other global objects, Math is not a constructor. All the properties and methods of Math are static and can be called by using Math as an object without creating it.

Thus, you refer to the constant pi as Math.PI and you call the sine function as Math.sin(x), where x is the method's argument.

Syntax

The syntax to call the properties and methods of Math are as follows

var pi_val = Math.PI;
var sine_val = Math.sin(30);

Math Properties

Here is a list of all the properties of Math and their description.

Sr.No. Property & Description
1 E

Euler's constant and the base of natural logarithms, approximately 2.718.

2 LN2

Natural logarithm of 2, approximately 0.693.

3 LN10

Natural logarithm of 10, approximately 2.302.

4 LOG2E

Base 2 logarithm of E, approximately 1.442.

5 LOG10E

Base 10 logarithm of E, approximately 0.434.

6 PI

Ratio of the circumference of a circle to its diameter, approximately 3.14159.

7 SQRT1_2

Square root of 1/2; equivalently, 1 over the square root of 2, approximately 0.707.

8 SQRT2

Square root of 2, approximately 1.414.

In the following sections, we will have a few examples to demonstrate the usage of Math properties.

Math Methods

Here is a list of the methods associated with Math object and their description

Sr.No. Method & Description
1 abs()

Returns the absolute value of a number.

2 acos()

Returns the arccosine (in radians) of a number.

3 asin()

Returns the arcsine (in radians) of a number.

4 atan()

Returns the arctangent (in radians) of a number.

5 atan2()

Returns the arctangent of the quotient of its arguments.

6 ceil()

Returns the smallest integer greater than or equal to a number.

7 cos()

Returns the cosine of a number.

8 exp()

Returns EN, where N is the argument, and E is Euler's constant, the base of the natural logarithm.

9 floor()

Returns the largest integer less than or equal to a number.

10 log()

Returns the natural logarithm (base E) of a number.

11 max()

Returns the largest of zero or more numbers.

12 min()

Returns the smallest of zero or more numbers.

13 pow()

Returns base to the exponent power, that is, base exponent.

14 random()

Returns a pseudo-random number between 0 and 1.

15 round()

Returns the value of a number rounded to the nearest integer.

16 sin()

Returns the sine of a number.

17 sqrt()

Returns the square root of a number.

18 tan()

Returns the tangent of a number.

19 toSource()

Returns the string "Math".

In the following sections, we will have a few examples to demonstrate the usage of the methods associated with Math.

Regular Expressions and RegExp Object

A regular expression is an object that describes a pattern of characters.

The JavaScript RegExp class represents regular expressions, and both String and RegExp define methods that use regular expressions to perform powerful pattern-matching and search-and-replace functions on text.

Syntax

A regular expression could be defined with the RegExp () constructor, as follows −

var pattern = new RegExp(pattern, attributes);
or simply
var pattern = /pattern/attributes;

Here is the description of the parameters −

  • pattern − A string that specifies the pattern of the regular expression or another regular expression.

  • attributes − An optional string containing any of the "g", "i", and "m" attributes that specify global, case-insensitive, and multi-line matches, respectively.

Brackets

Brackets ([]) have a special meaning when used in the context of regular expressions. They are used to find a range of characters.

Sr.No. Expression & Description
1

[...]

Any one character between the brackets.

2

[^...]

Any one character not between the brackets.

3

[0-9]

It matches any decimal digit from 0 through 9.

4

[a-z]

It matches any character from lowercase a through lowercase z.

5

[A-Z]

It matches any character from uppercase A through uppercase Z.

6

[a-Z]

It matches any character from lowercase a through uppercase Z.

The ranges shown above are general; you could also use the range [0-3] to match any decimal digit ranging from 0 through 3, or the range [b-v] to match any lowercase character ranging from b through v.

Quantifiers

The frequency or position of bracketed character sequences and single characters can be denoted by a special character. Each special character has a specific connotation. The +, *, ?, and $ flags all follow a character sequence.

Sr.No. Expression & Description
1

p+

It matches any string containing one or more p's.

2

p*

It matches any string containing zero or more p's.

3

p?

It matches any string containing at most one p.

4

p{N}

It matches any string containing a sequence of N p's

5

p{2,3}

It matches any string containing a sequence of two or three p's.

6

p{2, }

It matches any string containing a sequence of at least two p's.

7

p$

It matches any string with p at the end of it.

8

^p

It matches any string with p at the beginning of it.

Examples

Following examples explain more about matching characters.

Sr.No. Expression & Description
1

[^a-zA-Z]

It matches any string not containing any of the characters ranging from a through z and A through Z.

2

p.p

It matches any string containing p, followed by any character, in turn followed by another p.

3

^.{2}$

It matches any string containing exactly two characters.

4

<b>(.*)</b>

It matches any string enclosed within <b> and </b>.

5

p(hp)*

It matches any string containing a p followed by zero or more instances of the sequence hp.

Literal characters

Sr.No. Character & Description
1

Alphanumeric

Itself

2

HTML5 Tutorial

posted on May 28, 2021

tags:

HTML5 is the next major revision of the HTML standard superseding HTML 4.01, XHTML 1.0, and XHTML 1.1. HTML5 is a standard for structuring and presenting content on the World Wide Web.

HTML5 is a cooperation between the World Wide Web Consortium (W3C) and the Web Hypertext Application Technology Working Group (WHATWG).

The new standard incorporates features like video playback and drag-and-drop that have been previously dependent on third-party browser plug-ins such as Adobe Flash, Microsoft Silverlight, and Google Gears.

Browser Support

The latest versions of Apple Safari, Google Chrome, Mozilla Firefox, and Opera all support many HTML5 features and Internet Explorer 9.0 will also have support for some HTML5 functionality.

The mobile web browsers that come pre-installed on iPhones, iPads, and Android phones all have excellent support for HTML5.

New Features

HTML5 introduces a number of new elements and attributes that can help you in building modern websites. Here is a set of some of the most prominent features introduced in HTML5.

  • New Semantic Elements − These are like <header>, <footer>, and <section>.

  • Forms 2.0 − Improvements to HTML web forms where new attributes have been introduced for <input> tag.

  • Persistent Local Storage − To achieve without resorting to third-party plugins.

  • WebSocket − A next-generation bidirectional communication technology for web applications.

  • Server-Sent Events − HTML5 introduces events which flow from web server to the web browsers and they are called Server-Sent Events (SSE).

  • Canvas − This supports a two-dimensional drawing surface that you can program with JavaScript.

  • Audio & Video − You can embed audio or video on your webpages without resorting to third-party plugins.

  • Geolocation − Now visitors can choose to share their physical location with your web application.

  • Microdata − This lets you create your own vocabularies beyond HTML5 and extend your web pages with custom semantics.

  • Drag and drop − Drag and drop the items from one location to another location on the same webpage.

Backward Compatibility

HTML5 is designed, as much as possible, to be backward compatible with existing web browsers. Its new features have been built on existing features and allow you to provide fallback content for older browsers.

It is suggested to detect support for individual HTML5 features using a few lines of JavaScript.

If you are not familiar with any previous version of HTML, I would recommend that you go through our HTML Tutorial before exploring the features of HTML5.

HTML5 - Syntax

The HTML 5 language has a "custom" HTML syntax that is compatible with HTML 4 and XHTML1 documents published on the Web, but is not compatible with the more esoteric SGML features of HTML 4.

HTML 5 does not have the same syntax rules as XHTML where we needed lower case tag names, quoting our attributes, an attribute had to have a value and to close all empty elements.

HTML5 comes with a lot of flexibility and it supports the following features −

  • Uppercase tag names.
  • Quotes are optional for attributes.
  • Attribute values are optional.
  • Closing empty elements are optional.

The DOCTYPE

DOCTYPEs in older versions of HTML were longer because the HTML language was SGML based and therefore required a reference to a DTD.

HTML 5 authors would use simple syntax to specify DOCTYPE as follows −

<!DOCTYPE html>

The above syntax is case-insensitive.

Character Encoding

HTML 5 authors can use simple syntax to specify Character Encoding as follows −

<meta charset = "UTF-8">

The above syntax is case-insensitive.

The <script> tag

It's common practice to add a type attribute with a value of "text/javascript" to script elements as follows −

<script type = "text/javascript" src = "scriptfile.js"></script> 

HTML 5 removes extra information required and you can use simply following syntax −

<script src = "scriptfile.js"></script>

The <link> tag

So far you were writing <link> as follows −

<link rel = "stylesheet" type = "text/css" href = "stylefile.css">

HTML 5 removes extra information required and you can simply use the following syntax −

<link rel = "stylesheet" href = "stylefile.css">

HTML5 Elements

HTML5 elements are marked up using start tags and end tags. Tags are delimited using angle brackets with the tag name in between.

The difference between start tags and end tags is that the latter includes a slash before the tag name.

Following is the example of an HTML5 element −

<p>...</p>

HTML5 tag names are case insensitive and may be written in all uppercase or mixed case, although the most common convention is to stick with lowercase.

Most of the elements contain some content like <p>...</p> contains a paragraph. Some elements, however, are forbidden from containing any content at all and these are known as void elements. For example, br, hr, link, meta, etc.

Here is a complete list of HTML5 Elements.

HTML5 Attributes

Elements may contain attributes that are used to set various properties of an element.

Some attributes are defined globally and can be used on any element, while others are defined for specific elements only. All attributes have a name and a value and look like as shown below in the example.

Following is the example of an HTML5 attribute which illustrates how to mark up a div element with an attribute named class using a value of "example" −

<div class = "example">...</div>

Attributes may only be specified within start tags and must never be used in end tags.

HTML5 attributes are case insensitive and may be written in all uppercase or mixed case, although the most common convention is to stick with lowercase.

Here is a complete list of HTML5 Attributes.

HTML5 Document

The following tags have been introduced for better structure −

  • section − This tag represents a generic document or application section. It can be used together with h1-h6 to indicate the document structure.

  • article − This tag represents an independent piece of content of a document, such as a blog entry or newspaper article.

  • aside − This tag represents a piece of content that is only slightly related to the rest of the page.

  • header − This tag represents the header of a section.

  • footer − This tag represents a footer for a section and can contain information about the author, copyright information, et cetera.

  • nav − This tag represents a section of the document intended for navigation.

  • dialog − This tag can be used to mark up a conversation.

  • figure − This tag can be used to associate a caption together with some embedded content, such as a graphic or video.

The markup for an HTML 5 document would look like the following −

<!DOCTYPE html> 

<html>  
   <head> 
      <meta charset = "utf-8"> 
      <title>...</title> 
   </head> 
  
   <body> 
      <header>...</header> 
      <nav>...</nav> 
      
      <article> 
         <section> 
            ... 
         </section> 
      </article> 
      <aside>...</aside> 
      
      <footer>...</footer> 
   </body> 
</html> 

Live Demo

<!DOCTYPE html>  

<html>  
   <head> 
      <meta charset = "utf-8"> 
      <title>...</title> 
   </head> 
  
   <body> 
      <header role = "banner"> 
         <h1>HTML5 Document Structure Example</h1> 
         <p>This page should be tried in safari, chrome or Mozila.</p> 
      </header> 
   
      <nav> 
         <ul> 
            <li><a href = "https://www.tutorialspoint.com/html">HTML Tutorial</a></li> 
            <li><a href = "https://www.tutorialspoint.com/css">CSS Tutorial</a></li> 
            <li><a href = "https://www.tutorialspoint.com/javascript">
            JavaScript Tutorial</a></li> 
         </ul> 
      </nav> 
   
      <article> 
         <section> 
            <p>Once article can have multiple sections</p>
         </section> 
      </article> 
   
      <aside> 
         <p>This is  aside part of the web page</p> 
      </aside> 
   
      <footer> 
         <p>Created by <a href = "https://tutorialspoint.com/">Tutorials Point</a></p> 
      </footer> 
   
   </body> 
</html> 

It will produce the following result −

HTML5 - Attributes

As explained in the previous chapter, elements may contain attributes that are used to set various properties of an element.

Some attributes are defined globally and can be used on any element, while others are defined for specific elements only. All attributes have a name and a value and look like as shown below in the example.

Following is the example of an HTML5 attributes which illustrates how to mark up a div element with an attribute named class using a value of "example" −

<div class = "example">...</div>

Attributes may only be specified within start tags and must never be used in end tags.

HTML5 attributes are case insensitive and may be written in all uppercase or mixed case, although the most common convention is to stick with lowercase.

Standard Attributes

The attributes listed below are supported by almost all the HTML 5 tags.

Attribute Options Function
accesskey User Defined Specifies a keyboard shortcut to access an element.
align right, left, center Horizontally aligns tags
background URL Places an background image behind an element
bgcolor numeric, hexidecimal, RGB values Places a background color behind an element
class User Defined Classifies an element for use with Cascading Style Sheets.
contenteditable true, false Specifies if the user can edit the element's content or not.
contextmenu Menu id Specifies the context menu for an element.
data-XXXX User Defined Custom attributes. Authors of a HTML document can define their own attributes. Must start with "data-".
draggable true,false, auto Specifies whether or not a user is allowed to drag an element.
height Numeric Value Specifies the height of tables, images, or table cells.
hidden hidden Specifies whether element should be visible or not.
id User Defined Names an element for use with Cascading Style Sheets.
item List of elements Used to group elements.
itemprop List of items Used to group items.
spellcheck true, false Specifies if the element must have it's spelling or grammar checked.
style CSS Style sheet Specifies an inline style for an element.
subject User define id Specifies the element's corresponding item.
tabindex Tab number Specifies the tab order of an element.
title User Defined "Pop-up" title for your elements.
valign top, middle, bottom Vertically aligns tags within an HTML element.
width Numeric Value Specifies the width of tables, images, or table cells.

For a complete list of HTML5 Tags and related attributes, please check our reference to HTML5 Tags.

Custom Attributes

A new feature being introduced in HTML 5 is the addition of custom data attributes.

A custom data attribute starts with data- and would be named based on your requirement. Here is a simple example −

<div class = "example" data-subject = "physics" data-level = "complex">
   ...
</div>

The above code will be perfectly valid HTML5 with two custom attributes called datasubject and data-level. You would be able to get the values of these attributes using JavaScript APIs or CSS in similar way as you get for standard attributes.

HTML5 - Events

When users visit your website, they perform various activities such as clicking on text and images and links, hover over defined elements, etc. These are examples of what JavaScript calls events.

We can write our event handlers in Javascript or VBscript and you can specify these event handlers as a value of event tag attribute. The HTML5 specification defines various event attributes as listed below −

We can use the following set of attributes to trigger any javascript or vbscript code given as value, when there is any event that takes place for any HTML5 element.

We would cover element-specific events while discussing those elements in detail in subsequent chapters.

Attribute Value Description
offline script Triggers when the document goes offline
onabort script Triggers on an abort event
onafterprint script Triggers after the document is printed
onbeforeonload script Triggers before the document loads
onbeforeprint script Triggers before the document is printed
onblur script Triggers when the window loses focus
oncanplay script Triggers when media can start play, but might has to stop for buffering
oncanplaythrough script Triggers when media can be played to the end, without stopping for buffering
onchange script Triggers when an element changes
onclick script Triggers on a mouse click
oncontextmenu script Triggers when a context menu is triggered
ondblclick script Triggers on a mouse double-click
ondrag script Triggers when an element is dragged
ondragend script Triggers at the end of a drag operation
ondragenter script Triggers when an element has been dragged to a valid drop target
ondragleave script Triggers when an element leaves a valid drop target
ondragover script Triggers when an element is being dragged over a valid drop target
ondragstart script Triggers at the start of a drag operation
ondrop script Triggers when dragged element is being dropped
ondurationchange script Triggers when the length of the media is changed
onemptied script Triggers when a media resource element suddenly becomes empty.
onended script Triggers when media has reach the end
onerror script Triggers when an error occur
onfocus script Triggers when the window gets focus
onformchange script Triggers when a form changes
onforminput script Triggers when a form gets user input
onhaschange script Triggers when the document has change
oninput script Triggers when an element gets user input
oninvalid script Triggers when an element is invalid
onkeydown script Triggers when a key is pressed
onkeypress script Triggers when a key is pressed and released
onkeyup script Triggers when a key is released
onload script Triggers when the document loads
onloadeddata script Triggers when media data is loaded
onloadedmetadata script Triggers when the duration and other media data of a media element is loaded
onloadstart script Triggers when the browser starts to load the media data
onmessage script Triggers when the message is triggered
onmousedown script Triggers when a mouse button is pressed
onmousemove script Triggers when the mouse pointer moves
onmouseout script Triggers when the mouse pointer moves out of an element
onmouseover script Triggers when the mouse pointer moves over an element
onmouseup script Triggers when a mouse button is released
onmousewheel script Triggers when the mouse wheel is being rotated
onoffline script Triggers when the document goes offline
onoine script Triggers when the document comes online
ononline script Triggers when the document comes online
onpagehide script Triggers when the window is hidden
onpageshow script Triggers when the window becomes visible
onpause script Triggers when media data is paused
onplay script Triggers when media data is going to start playing
onplaying script Triggers when media data has start playing
onpopstate script Triggers when the window's history changes
onprogress script Triggers when the browser is fetching the media data
onratechange script Triggers when the media data's playing rate has changed
onreadystatechange script Triggers when the ready-state changes
onredo script Triggers when the document performs a redo
onresize script Triggers when the window is resized
onscroll script Triggers when an element's scrollbar is being scrolled
onseeked script Triggers when a media element's seeking attribute is no longer true, and the seeking has ended
onseeking script Triggers when a media element's seeking attribute is true, and the seeking has begun
onselect script Triggers when an element is selected
onstalled script Triggers when there is an error in fetching media data
onstorage script Triggers when a document loads
onsubmit script Triggers when a form is submitted
onsuspend script Triggers when the browser has been fetching media data, but stopped before the entire media file was fetched
ontimeupdate script Triggers when media changes its playing position
onundo script Triggers when a document performs an undo
onunload script Triggers when the user leaves the document
onvolumechange script Triggers when media changes the volume, also when volume is set to "mute"
onwaiting script Triggers when media has stopped playing, but is expected to resume

HTML5 - Web Forms 2.0

Web Forms 2.0 is an extension to the forms features found in HTML4. Form elements and attributes in HTML5 provide a greater degree of semantic mark-up than HTML4 and free us from a great deal of tedious scripting and styling that was required in HTML4.

The <input> element in HTML4

HTML4 input elements use the type attribute to specify the data type.HTML4 provides following types −

Sr.No. Type & Description
1

text

A free-form text field, nominally free of line breaks.

2

password

A free-form text field for sensitive information, nominally free of line breaks.

3

checkbox

A set of zero or more values from a predefined list.

4

radio

An enumerated value.

5

submit

A free form of button initiates form submission.

6

file

An arbitrary file with a MIME type and optionally a file name.

7

image

A coordinate, relative to a particular image's size, with the extra semantic that it must be the last value selected and initiates form submission.

8

hidden

An arbitrary string that is not normally displayed to the user.

9

select

An enumerated value, much like the radio type.

10

textarea

A free-form text field, nominally with no line break restrictions.

11

button

A free form of button which can initiates any event related to button.

Following is the simple example of using labels, radio buttons, and submit buttons −

... 
<form action = "http://example.com/cgiscript.pl" method = "post">  
   <p> 
      <label for = "firstname">first name: </label> 
      <input type = "text" id = "firstname"><br /> 
   
      <label for = "lastname">last name: </label> 
      <input type = "text" id = "lastname"><br /> 
   
      <label for = "email">email: </label> 
      <input type = "text" id = "email"><br> 
   
      <input type = "radio" name = "sex" value = "male"> Male<br> 
      <input type = "radio" name = "sex" value = "female"> Female<br> 
      <input type = "submit" value = "send"> <input type = "reset"> 
   </p> 
</form> 
 ... 

The <input> element in HTML5

Apart from the above-mentioned attributes, HTML5 input elements introduced several new values for the type attribute. These are listed below.

NOTE − Try all the following example using latest version of Opera browser.

Sr.No. Type & Description
1 datetime

A date and time (year, month, day, hour, minute, second, fractions of a second) encoded according to ISO 8601 with the time zone set to UTC.

2 datetime-local

A date and time (year, month, day, hour, minute, second, fractions of a second) encoded according to ISO 8601, with no time zone information.

3 date

A date (year, month, day) encoded according to ISO 8601.

4 month

A date consisting of a year and a month encoded according to ISO 8601.

5 week

A date consisting of a year and a week number encoded according to ISO 8601.

6 time

A time (hour, minute, seconds, fractional seconds) encoded according to ISO 8601.

7 number

It accepts only numerical value. The step attribute specifies the precision, defaulting to 1.

8 range

The range type is used for input fields that should contain a value from a range of numbers.

9 email

It accepts only email value. This type is used for input fields that should contain an e-mail address. If you try to submit a simple text, it forces to enter only email address in email@example.com format.

10 url

It accepts only URL value. This type is used for input fields that should contain a URL address. If you try to submit a simple text, it forces to enter only URL address either in http://www.example.com format or in http://example.com format.

The <output> element

HTML5 introduced a new element <output> which is used to represent the result of different types of output, such as output written by a script.

You can use the for attribute to specify a relationship between the output element and other elements in the document that affected the calculation (for example, as inputs or parameters). The value of the for attribute is a space-separated list of IDs of other elements.

Live Demo

<!DOCTYPE HTML>

<html>
   <head>
      <script type = "text/javascript">
         
         function showResult() {
            x = document.forms["myform"]["newinput"].value;
            document.forms["myform"]["result"].value = x;
         }
      </script>
   </head>
   
   <body>

      <form action = "/cgi-bin/html5.cgi" method = "get" name = "myform">
         Enter a value : <input type = "text" name = "newinput" />
         <input type = "button" value = "Result"  onclick = "showResult();" />
         <output name = "result"></output>
      </form>
		
   </body>
</html>

It will produce the following result −

The placeholder attribute

HTML5 introduced a new attribute called placeholder. This attribute on <input> and <textarea> elements provide a hint to the user of what can be entered in the field. The placeholder text must not contain carriage returns or line-feeds.

Here is the simple syntax for placeholder attribute −

<input type = "text" name = "search" placeholder = "search the web"/>

This attribute is supported by latest versions of Mozilla, Safari and Crome browsers only.

Live Demo

<!DOCTYPE HTML>

<html>
   <body>

      <form action = "/cgi-bin/html5.cgi" method = "get">
         Enter email : <input type = "email" name = "newinput" 
            placeholder = "email@example.com"/>
         <input type = "submit" value = "submit" />
      </form>

   </body>
</html>

This will produce the following result −

The autofocus attribute

This is a simple one-step pattern, easily programmed in JavaScript at the time of document load, automatically focus one particular form field.

HTML5 introduced a new attribute called autofocus which would be used as follows −

<input type = "text" name = "search" autofocus/>

This attribute is supported by latest versions of Mozilla, Safari and Chrome browsers only.

<!DOCTYPE HTML>

<html>
   <body>
   
      <form action = "/cgi-bin/html5.cgi" method = "get">
         Enter email : <input type = "text" name = "newinput" autofocus/>
         <p>Try to submit using Submit button</p>
         <input type = "submit" value = "submit" />
      </form>
      
   </body>
</html>

The required attribute

Now you do not need to have JavaScript for client-side validations like empty text box would never be submitted because HTML5 introduced a new attribute called required which would be used as follows and would insist to have a value −

<input type = "text" name = "search" required/>

This attribute is supported by latest versions of Mozilla, Safari and Chrome browsers only.

Live Demo

<!DOCTYPE HTML>

<html>
   <body>
   
      <form action = "/cgi-bin/html5.cgi" method = "get">
         Enter email : <input type = "text" name = "newinput" required/>
         <p>Try to submit using Submit button</p>
         <input type = "submit" value = "submit" />
      </form>
      
   </body>
</html>

It will produce the following result −

HTML5 - SVG

SVG stands for Scalable Vector Graphics and it is a language for describing 2D-graphics and graphical applications in XML and the XML is then rendered by an SVG viewer.

SVG is mostly useful for vector type diagrams like Pie charts, Two-dimensional graphs in an X,Y coordinate system etc.

SVG became a W3C Recommendation 14. January 2003 and you can check latest version of SVG specification at SVG Specification.

Viewing SVG Files

Most of the web browsers can display SVG just like they can display PNG, GIF, and JPG. Internet Explorer users may have to install the Adobe SVG Viewer to be able to view SVG in the browser.

Embedding SVG in HTML5

HTML5 allows embedding SVG directly using <svg>...</svg> tag which has following simple syntax −

<svg xmlns = "http://www.w3.org/2000/svg">
   ...    
</svg>

Firefox 3.7 has also introduced a configuration option ("about:config") where you can enable HTML5 using the following steps −

  • Type about:config in your Firefox address bar.

  • Click the "I'll be careful, I promise!" button on the warning message that appears (and make sure you adhere to it!).

  • Type html5.enable into the filter bar at the top of the page.

  • Currently it would be disabled, so click it to toggle the value to true.

Now your Firefox HTML5 parser should be enabled and you should be able to experiment with the following examples.

HTML5 − SVG Circle

Following is the HTML5 version of an SVG example which would draw a circle using <circle> tag −

Live Demo

<!DOCTYPE html>

<html>
   <head>
   
      <style>
         #svgelem {
            position: relative;
            left: 50%;
            -webkit-transform: translateX(-20%);
            -ms-transform: translateX(-20%);
            transform: translateX(-20%);
         }
      </style>
      <title>SVG</title>
      <meta charset = "utf-8" />
   </head>
   
   <body>
      <h2 align = "center">HTML5 SVG Circle</h2>
		
      <svg id = "svgelem" height = "200" xmlns = "http://www.w3.org/2000/svg">
         <circle id = "redcircle" cx = "50" cy = "50" r = "50" fill = "red" />
      </svg>
   </body>
</html>

This would produce the following result in HTML5 enabled latest version of Firefox.

HTML5 − SVG Rectangle

Following is the HTML5 version of an SVG example which would draw a rectangle using <rect> tag −

Live Demo

<!DOCTYPE html>

<html>
   <head>
   
      <style>
         #svgelem {
            position: relative;
            left: 50%;
            -webkit-transform: translateX(-50%);
            -ms-transform: translateX(-50%);
            transform: translateX(-50%);
         }
      </style>
      <title>SVG</title>
      <meta charset = "utf-8" />
   </head>
   
   <body>
      <h2 align = "center">HTML5 SVG Rectangle</h2>
      
      <svg id = "svgelem" height = "200" xmlns = "http://www.w3.org/2000/svg">
         <rect id = "redrect" width = "300" height = "100" fill = "red" />
      </svg>
   </body>
</html>

This would produce the following result in HTML5 enabled latest version of Firefox.

HTML5 − SVG Line

Following is the HTML5 version of an SVG example which would draw a line using <line> tag −

Live Demo

<!DOCTYPE html>

<html>
   <head>
      
      <style>
         #svgelem {
            position: relative;
            left: 50%;
            -webkit-transform: translateX(-50%);
            -ms-transform: translateX(-50%);
            transform: translateX(-50%);
         }
      </style>
      <title>SVG</title>
      <meta charset = "utf-8" />
   </head>
   
   <body>
      <h2 align = "center">HTML5 SVG Line</h2>
      
      <svg id = "svgelem" height = "200" xmlns = "http://www.w3.org/2000/svg">
         <line x1 = "0" y1 = "0" x2 = "200" y2 = "100" 
            style = "stroke:red;stroke-width:2"/>
      </svg>
   </body>
</html>

You can use the style attribute which allows you to set additional style information like stroke and fill colors, width of the stroke, etc.

This would produce the following result in HTML5 enabled latest version of Firefox.

HTML5 − SVG Ellipse

Following is the HTML5 version of an SVG example which would draw an ellipse using <ellipse> tag −

Live Demo

<!DOCTYPE html>

<html>
   <head>
      
      <style>
         #svgelem {
            position: relative;
            left: 50%;
            -webkit-transform: translateX(-40%);
            -ms-transform: translateX(-40%);
            transform: translateX(-40%);
         }
      </style>
      <title>SVG</title>
      <meta charset = "utf-8" />
   </head>
	
   <body>
      <h2 align = "center">HTML5 SVG Ellipse</h2>
      
      <svg id = "svgelem" height = "200" xmlns = "http://www.w3.org/2000/svg">
         <ellipse cx = "100" cy = "50" rx = "100" ry = "50" fill = "red" />
      </svg>
		
   </body>
</html>

This would produce the following result in HTML5 enabled latest version of Firefox.

HTML5 − SVG Polygon

Following is the HTML5 version of an SVG example which would draw a polygon using <polygon> tag −

Live Demo

<!DOCTYPE html>

<html>
   <head>
   
      <style>
         #svgelem {
            position: relative;
            left: 50%;
            -webkit-transform: translateX(-50%);
            -ms-transform: translateX(-50%);
            transform: translateX(-50%);
         }
      </style>
      <title>SVG</title>
      <meta charset = "utf-8" />
   </head>
	
   <body>
      <h2 align = "center">HTML5 SVG Polygon</h2>
      
      <svg id = "svgelem" height = "200" xmlns = "http://www.w3.org/2000/svg">
         <polygon  points = "20,10 300,20, 170,50" fill = "red" />
      </svg>
   </body>
</html>

This would produce the following result in HTML5 enabled latest version of Firefox.

HTML5 − SVG Polyline

Following is the HTML5 version of an SVG example which would draw a polyline using <polyline> tag −

Live Demo

<!DOCTYPE html>

<html>
   <head>
      
      <style>
         #svgelem {
            position: relative;
            left: 50%;
            -webkit-transform: translateX(-20%);
            -ms-transform: translateX(-20%);
            transform: translateX(-20%);
         }
      </style>
      <title>SVG</title>
      <meta charset = "utf-8" />
   </head>
	
   <body>
      <h2 align = "center">HTML5 SVG Polyline</h2>
      <svg id = "svgelem" height = "200" xmlns = "http://www.w3.org/2000/svg">
         <polyline points = "0,0 0,20 20,20 20,40 40,40 40,60" fill = "red" />
      </svg>
   </body>
</html>

This would produce the following result in HTML5 enabled latest version of Firefox.

HTML5 − SVG Gradients

Following is the HTML5 version of an SVG example which would draw an ellipse using <ellipse> tag and would use <radialGradient> tag to define an SVG radial gradient.

Similarly, you can use <linearGradient> tag to create SVG linear gradient.

Live Demo

<!DOCTYPE html>

<html>
   <head>
      
      <style>
         #svgelem {
            position: relative;
            left: 50%;
            -webkit-transform: translateX(-40%);
            -ms-transform: translateX(-40%);
            transform: translateX(-40%);
         }
      </style>
      <title>SVG</title>
      <meta charset = "utf-8" />
   </head>
	
   <body>
      <h2 align = "center">HTML5 SVG Gradient Ellipse</h2>
      
      <svg id = "svgelem" height = "200" xmlns = "http://www.w3.org/2000/svg">
         <defs>
            <radialGradient id="gradient" cx = "50%" cy = "50%" r = "50%" fx = "50%" 
               fy = "50%">
               <stop offset = "0%" style = "stop-color:rgb(200,200,200); stop-opacity:0"/>
               <stop offset = "100%" style = "stop-color:rgb(0,0,255); stop-opacity:1"/>
            </radialGradient>
         </defs>
         <ellipse cx = "100" cy = "50" rx = "100" ry = "50" 
            style = "fill:url(#gradient)" />
      </svg>
		
   </body>
</html>

This would produce the following result in HTML5 enabled latest version of Firefox.

HTML5 − SVG Star

Following is the HTML5 version of an SVG example which would draw a star using <polygon> tag.

Live Demo

<html>
   <head>
   
      <style>
         #svgelem {
            position: relative;
            left: 50%;
            -webkit-transform: translateX(-40%);
            -ms-transform: translateX(-40%);
            transform: translateX(-40%);
         }
      </style>
      <title>SVG</title>
      <meta charset = "utf-8" />
   </head>
   
   <body>	
      <h2 align = "center">HTML5 SVG Star</h2>
      
      <svg id = "svgelem" height = "200" xmlns = "http://www.w3.org/2000/svg">
         <polygon points = "100,10 40,180 190,60 10,60 160,180" fill = "red"/>
      </svg>
    </body>
</html>

This would produce the following result in HTML5 enabled latest version of Firefox.

HTML5 - MathML

The HTML syntax of HTML5 allows for MathML elements to be used inside a document using <math>...</math> tags.

Most of the web browsers can display MathML tags. If your browser does not support MathML, then I would suggest you to use latest version of Firefox.

MathML Examples

Following is a valid HTML5 document with MathML −

Live Demo

<!doctype html>

<html>
   <head>
      <meta charset = "UTF-8">
      <title>Pythagorean theorem</title>
   </head>
	
   <body>
      <math xmlns = "http://www.w3.org/1998/Math/MathML">
		
         <mrow>
            <msup><mi>a</mi><mn>2</mn></msup>
            <mo>+</mo>
				
            <msup><mi>b</mi><mn>2</mn></msup>
            <mo> = </mo>
				
            <msup><mi>c</mi><mn>2</mn></msup>
         </mrow>
			
      </math>
   </body>
</html> 

This will produce the following result −

Using MathML Characters

Consider, following is the markup which makes use of the characters &InvisibleTimes; −

Live Demo

<!doctype html>

<html>
   <head>
      <meta charset = "UTF-8">
      <title>MathML Examples</title>
   </head>
	
   <body>
      <math xmlns = "http://www.w3.org/1998/Math/MathML">
		
         <mrow>			
            <mrow>
				
               <msup>
                  <mi>x</mi>
                  <mn>2</mn>
               </msup>
					
               <mo>+</mo>
					
               <mrow>
                  <mn>4</mn>
                  <mo>â¢</mo>
                  <mi>x</mi>
               </mrow>
					
               <mo>+</mo>
               <mn>4</mn>
					
            </mrow>
				
            <mo>=</mo>
            <mn>0</mn>
				 
         </mrow>
      </math>
   </body>
</html> 

This would produce the following result. If you are not able to see proper result like x2 + 4x + 4 = 0, then use Firefox 3.5 or higher version.

This will produce the following result −

Matrix Presentation Examples

Consider the following example which would be used to represent a simple 2x2 matrix −

Live Demo

<!doctype html>

<html>
   <head>
      <meta charset = "UTF-8">
      <title>MathML Examples</title>
   </head>
	
   <body>
      <math xmlns = "http://www.w3.org/1998/Math/MathML">
		
         <mrow>
            <mi>A</mi>
            <mo>=</mo>
			
            <mfenced open = "[" close="]">
			
               <mtable>
                  <mtr>
                     <mtd><mi>x</mi></mtd>
                     <mtd><mi>y</mi></mtd>
                  </mtr>
					
                  <mtr>
                     <mtd><mi>z</mi></mtd>
                     <mtd><mi>w</mi></mtd>
                  </mtr>
               </mtable>
               
            </mfenced>
         </mrow>
      </math>

   </body>
</html> 

This will produce the following result −

This would produce the following result. If you are not able to see proper result, then use Firefox 3.5 or higher version.

MathML

HTML5 - Web Storage

HTML5 introduces two mechanisms, similar to HTTP session cookies, for storing structured data on the client side and to overcome following drawbacks.

  • Cookies are included with every HTTP request, thereby slowing down your web application by transmitting the same data.

  • Cookies are included with every HTTP request, thereby sending data unencrypted over the internet.

  • Cookies are limited to about 4 KB of data. Not enough to store required data.

The two storages are session storage and local storage and they would be used to handle different situations.

The latest versions of pretty much every browser supports HTML5 Storage including Internet Explorer.

Session Storage

The Session Storage is designed for scenarios where the user is carrying out a single transaction, but could be carrying out multiple transactions in different windows at the same time.

Example

For example, if a user buying plane tickets in two different windows, using the same site. If the site used cookies to keep track of which ticket the user was buying, then as the user clicked from page to page in both windows, the ticket currently being purchased would "leak" from one window to the other, potentially causing the user to buy two tickets for the same flight without really noticing.

HTML5 introduces the sessionStorage attribute which would be used by the sites to add data to the session storage, and it will be accessible to any page from the same site opened in that window, i.e., session and as soon as you close the window, the session would be lost.

Following is the code which would set a session variable and access that variable −

Live Demo

<!DOCTYPE HTML>

<html>
   <body>
      <script type = "text/javascript">
         
         if( sessionStorage.hits ) {
            sessionStorage.hits = Number(sessionStorage.hits) +1;
         } else {
            sessionStorage.hits = 1;
         }
         document.write("Total Hits :" + sessionStorage.hits );
      </script>
	
      <p>Refresh the page to increase number of hits.</p>
      <p>Close the window and open it again and check the result.</p>

   </body>
</html>

This will produce the following result −

Local Storage

The Local Storage is designed for storage that spans multiple windows, and lasts beyond the current session. In particular, Web applications may wish to store megabytes of user data, such as entire user-authored documents or a user's mailbox, on the client side for performance reasons.

Again, cookies do not handle this case well, because they are transmitted with every request.

Example

HTML5 introduces the localStorage attribute which would be used to access a page's local storage area without no time limit and this local storage will be available whenever you would use that page.

Following is the code which would set a local storage variable and access that variable every time this page is accessed, even next time, when you open the window −

Live Demo

<!DOCTYPE HTML>

<html>
   <body>
      <script type = "text/javascript">
         
         if( localStorage.hits ) {
            localStorage.hits = Number(localStorage.hits) +1;
         } else {
            localStorage.hits = 1;
         }
         document.write("Total Hits :" + localStorage.hits );
      </script>
		
      <p>Refresh the page to increase number of hits.</p>
      <p>Close the window and open it again and check the result.</p>

   </body>
</html>

This will produce the following result −

Delete Web Storage

Storing sensitive data on local machine could be dangerous and could leave a security hole.

The Session Storage Data would be deleted by the browsers immediately after the session gets terminated.

To clear a local storage setting you would need to call localStorage.remove('key'); where 'key' is the key of the value you want to remove. If you want to clear all settings, you need to call localStorage.clear() method.

Following is the code which would clear complete local storage −

Live Demo

<!DOCTYPE HTML>

<html>
   <body>

      <script type = "text/javascript">
         localStorage.clear();

         // Reset number of hits.
         if( localStorage.hits ) {
            localStorage.hits = Number(localStorage.hits) +1;
         } else {
            localStorage.hits = 1;
         }
         document.write("Total Hits :" + localStorage.hits );
			
      </script>
		
      <p>Refreshing the page would not to increase hit counter.</p>
      <p>Close the window and open it again and check the result.</p>

   </body>
</html>

This will produce following result −

HTML5 - Web SQL Database

The Web SQL Database API isn't actually part of the HTML5 specification but it is a separate specification which introduces a set of APIs to manipulate client-side databases using SQL.

I'm assuming you are a great web developer and if that is the case then no doubt, you would be well aware of SQL and RDBMS concepts. If you still want to have a session with SQL then, you can go through our SQL Tutorial.

Web SQL Database will work in latest version of Safari, Chrome and Opera.

The Core Methods

There are following three core methods defined in the spec that I am going to cover in this tutorial −

  • openDatabase − This method creates the database object either using existing database or creating new one.

  • transaction − This method gives us the ability to control a transaction and performing either commit or rollback based on the situation.

  • executeSql − This method is used to execute actual SQL query.

Opening Database

The openDatabase method takes care of opening a database if it already exists, this method will create it if it already does not exist.

To create and open a database, use the following code −

var db = openDatabase('mydb', '1.0', 'Test DB', 2 * 1024 * 1024);

The above method took the following five parameters −

  • Database name
  • Version number
  • Text description
  • Size of database
  • Creation callback

The last and 5th argument, creation callback will be called if the database is being created. Without this feature, however, the databases are still being created on the fly and correctly versioned.

Executing queries

To execute a query you use the database.transaction() function. This function needs a single argument, which is a function that takes care of actually executing the query as follows −

var db = openDatabase('mydb', '1.0', 'Test DB', 2 * 1024 * 1024); 

db.transaction(function (tx) {   
   tx.executeSql('CREATE TABLE IF NOT EXISTS LOGS (id unique, log)'); 
});

The above query will create a table called LOGS in 'mydb' database.

INSERT Operation

To create enteries into the table we add simple SQL query in the above example as follows −

var db = openDatabase('mydb', '1.0', 'Test DB', 2 * 1024 * 1024); 

db.transaction(function (tx) { 
   tx.executeSql('CREATE TABLE IF NOT EXISTS LOGS (id unique, log)'); 
   tx.executeSql('INSERT INTO LOGS (id, log) VALUES (1, "foobar")'); 
   tx.executeSql('INSERT INTO LOGS (id, log) VALUES (2, "logmsg")'); 
}); 

We can pass dynamic values while creating entering as follows −

var db = openDatabase('mydb', '1.0', 'Test DB', 2 * 1024 * 1024);  

db.transaction(function (tx) {   
   tx.executeSql('CREATE TABLE IF NOT EXISTS LOGS (id unique, log)'); 
   tx.executeSql('INSERT INTO LOGS (id,log) VALUES (?, ?'), [e_id, e_log]; 
});

Here e_id and e_log are external variables, and executeSql maps each item in the array argument to the "?"s.

READ Operation

To read already existing records we use a callback to capture the results as follows −

var db = openDatabase('mydb', '1.0', 'Test DB', 2 * 1024 * 1024);  

db.transaction(function (tx) { 
   tx.executeSql('CREATE TABLE IF NOT EXISTS LOGS (id unique, log)');
   tx.executeSql('INSERT INTO LOGS (id, log) VALUES (1, "foobar")'); 
   tx.executeSql('INSERT INTO LOGS (id, log) VALUES (2, "logmsg")'); 
});  

db.transaction(function (tx) { 
   tx.executeSql('SELECT * FROM LOGS', [], function (tx, results) { 
      var len = results.rows.length, i; 
      msg = "<p>Found rows: " + len + "</p>"; 
      document.querySelector('#status').innerHTML +=  msg; 
  
      for (i = 0; i < len; i++) { 
         alert(results.rows.item(i).log ); 
      } 
  
   }, null); 
});

Final Example

So finally, let us keep this example in a full-fledged HTML5 document as follows and try to run it with Safari browser.

Live Demo

<!DOCTYPE HTML> 

<html>  
   <head> 
  
      <script type = "text/javascript"> 
         var db = openDatabase('mydb', '1.0', 'Test DB', 2 * 1024 * 1024); 
         var msg; 
    
         db.transaction(function (tx) { 
            tx.executeSql('CREATE TABLE IF NOT EXISTS LOGS (id unique, log)'); 
            tx.executeSql('INSERT INTO LOGS (id, log) VALUES (1, "foobar")'); 
            tx.executeSql('INSERT INTO LOGS (id, log) VALUES (2, "logmsg")'); 
            msg = '<p>Log message created and row inserted.</p>'; 
            document.querySelector('#status').innerHTML =  msg; 
         })

         db.transaction(function (tx) { 
            tx.executeSql('SELECT * FROM LOGS', [], function (tx, results) { 
               var len = results.rows.length, i; 
               msg = "<p>Found rows: " + len + "</p>"; 
               document.querySelector('#status').innerHTML +=  msg; 
      
               for (i = 0; i < len; i++) { 
                  msg = "<p><b>" + results.rows.item(i).log + "</b></p>"; 
                  document.querySelector('#status').innerHTML +=  msg; 
               } 
            }, null); 
         }); 
      </script> 
   </head> 
  
   <body> 
      <div id = "status" name = "status">Status Message</div> 
   </body> 
</html>

This will produce the following result −

HTML5 - Server Sent Events

Conventional web applications generate events which are dispatched to the web server. For example, a simple click on a link requests a new page from the server.

The type of events which are flowing from web browser to the web server may be called client-sent events.

Along with HTML5, WHATWG Web Applications 1.0 introduces events which flow from web server to the web browsers and they are called Server-Sent Events (SSE). Using SSE you can push DOM events continuously from your web server to the visitor's browser.

The event streaming approach opens a persistent connection to the server, sending data to the client when new information is available, eliminating the need for continuous polling.

Server-sent events standardize how we stream data from the server to the client.

Web Application for SSE

To use Server-Sent Events in a web application, you would need to add an <eventsource> element to the document.

The src attribute of <eventsource> element should point to an URL which should provide a persistent HTTP connection that sends a data stream containing the events.

The URL would point to a PHP, PERL or any Python script which would take care of sending event data consistently. Following is a simple example of web application which would expect server time.

<!DOCTYPE HTML>

<html>
   <head>
   
      <script type = "text/javascript">
         /* Define event handling logic here */
      </script>
   </head>
   
   <body>
      <div id = "sse">
         <eventsource src = "/cgi-bin/ticker.cgi" />
      </div>
		
      <div id = "ticker">
         <TIME>
      </div>
   </body>
</html>

Server Side Script for SSE

A server side script should send Content-type header specifying the type text/event-stream as follows.

print "Content-Type: text/event-stream

";

After setting Content-Type, server side script would send an Event: tag followed by event name. Following example would send Server-Time as event name terminated by a new line character.

print "Event: server-time
";

Final step is to send event data using Data: tag which would be followed by integer of string value terminated by a new line character as follows −

$time = localtime();
print "Data: $time
";

Finally, following is complete ticker.cgi written in Perl −

#!/usr/bin/perl  
print "Content-Type: text/event-stream

";  

while(true) { 
   print "Event: server-time
"; 
   $time = localtime(); 
   print "Data: $time
"; 
   sleep(5); 
} 

Handle Server-Sent Events

Let us modify our web application to handle server-sent events. Following is the final example.

<!DOCTYPE HTML> 

<html>  
   <head> 
  
      <script type = "text/javascript"> 
         document.getElementsByTagName("eventsource")[0].addEventListener("server-time", 
         eventHandler, false); 
    
         function eventHandler(event) { 

            // Alert time sent by the server 
            document.querySelector('#ticker').innerHTML = event.data; 
         } 
      </script> 
   </head> 
  
   <body> 
      <div id = "sse"> 
         <eventsource src = "/cgi-bin/ticker.cgi" /> 
      </div> 
   
      <div id = "ticker" name = "ticker"> 
         [TIME] 
      </div> 
   </body> 
</html>

Before testing Server-Sent events, I would suggest that you make sure your web browser supports this concept.

HTML5 - WebSockets

WebSockets is a next-generation bidirectional communication technology for web applications which operates over a single socket and is exposed via a JavaScript interface in HTML 5 compliant browsers.

Once you get a Web Socket connection with the web server, you can send data from browser to server by calling a send() method, and receive data from server to browser by an onmessage event handler.

Following is the API which creates a new WebSocket object.

var Socket = new WebSocket(url, [protocal] );

Here first argument, url, specifies the URL to which to connect. The second attribute, protocol is optional, and if present, specifies a sub-protocol that the server must support for the connection to be successful.

WebSocket Attributes

Following are the attribute of WebSocket object. Assuming we created Socket object as mentioned above −

Sr.No. Attribute & Description
1

Socket.readyState

The readonly attribute readyState represents the state of the connection. It can have the following values −

  • A value of 0 indicates that the connection has not yet been established.

  • A value of 1 indicates that the connection is established and communication is possible.

  • A value of 2 indicates that the connection is going through the closing handshake.

  • A value of 3 indicates that the connection has been closed or could not be opened.

2

Socket.bufferedAmount

The readonly attribute bufferedAmount represents the number of bytes of UTF-8 text that have been queued using send() method.

WebSocket Events

Following are the events associated with WebSocket object. Assuming we created Socket object as mentioned above −

Event Event Handler Description
open Socket.onopen This event occurs when socket connection is established.
message Socket.onmessage This event occurs when client receives data from server.
error Socket.onerror This event occurs when there is any error in communication.
close Socket.onclose This event occurs when connection is closed.

WebSocket Methods

Following are the methods associated with WebSocket object. Assuming we created Socket object as mentioned above −

Sr.No. Method & Description
1

Socket.send()

The send(data) method transmits data using the connection.

2

Socket.close()

The close() method would be used to terminate any existing connection.

WebSocket Example

A WebSocket is a standard bidirectional TCP socket between the client and the server. The socket starts out as a HTTP connection and then "Upgrades" to a TCP socket after a HTTP handshake. After the handshake, either side can send data.

Client Side HTML & JavaScript Code

At the time of writing this tutorial, there are only few web browsers supporting WebSocket() interface. You can try following example with latest version of Chrome, Mozilla, Opera and Safari.

<!DOCTYPE HTML>

<html>
   <head>
      
      <script type = "text/javascript">
         function WebSocketTest() {
            
            if ("WebSocket" in window) {
               alert("WebSocket is supported by your Browser!");
               
               // Let us open a web socket
               var ws = new WebSocket("ws://localhost:9998/echo");
				
               ws.onopen = function() {
                  
                  // Web Socket is connected, send data using send()
                  ws.send("Message to send");
                  alert("Message is sent...");
               };
				
               ws.onmessage = function (evt) { 
                  var received_msg = evt.data;
                  alert("Message is received...");
               };
				
               ws.onclose = function() { 
                  
                  // websocket is closed.
                  alert("Connection is closed..."); 
               };
            } else {
              
               // The browser doesn't support WebSocket
               alert("WebSocket NOT supported by your Browser!");
            }
         }
      </script>
		
   </head>
   
   <body>
      <div id = "sse">
         <a href = "javascript:WebSocketTest()">Run WebSocket</a>
      </div>
      
   </body>
</html>

Install pywebsocket

Before you test above client program, you need a server which supports WebSocket. Download mod_pywebsocket-x.x.x.tar.gz from pywebsocket which aims to provide a Web Socket extension for Apache HTTP Server and install it following these steps.

  • Unzip and untar the downloaded file.

  • Go inside pywebsocket-x.x.x/src/ directory.

  • $python setup.py build

  • $sudo python setup.py install

  • Then read document by −

    • $pydoc mod_pywebsocket

This will install it into your python environment.

Start the Server

Go to the pywebsocket-x.x.x/src/mod_pywebsocket folder and run the following command −

$sudo python standalone.py -p 9998 -w ../example/

This will start the server listening at port 9998 and use the handlers directory specified by the -w option where our echo_wsh.py resides.

Now using Chrome browser open the html file your created in the beginning. If your browser supports WebSocket(), then you would get alert indicating that your browser supports WebSocket and finally when you click on "Run WebSocket" you would get Goodbye message sent by the server script.

HTML5 - Canvas

HTML5 element <canvas> gives you an easy and powerful way to draw graphics using JavaScript. It can be used to draw graphs, make photo compositions or do simple (and not so simple) animations.

Here is a simple <canvas> element which has only two specific attributes width and height plus all the core HTML5 attributes like id, name and class, etc.

<canvas id = "mycanvas" width = "100" height = "100"></canvas>

You can easily find that <canvas> element in the DOM using getElementById() method as follows −

var canvas = document.getElementById("mycanvas");

Let us see a simple example on using <canvas> element in HTML5 document.

Live Demo

<!DOCTYPE HTML>

<html>
   <head>
   
      <style>
         #mycanvas{border:1px solid red;}
      </style>
   </head>
   
   <body>
      <canvas id = "mycanvas" width = "100" height = "100"></canvas>
   </body>
</html>

This will produce the following result −

The Rendering Context

The <canvas> is initially blank, and to display something, a script first needs to access the rendering context and draw on it.

The canvas element has a DOM method called getContext, used to obtain the rendering context and its drawing functions. This function takes one parameter, the type of context2d.

Following is the code to get required context along with a check if your browser supports <canvas> element −

var canvas  = document.getElementById("mycanvas");

if (canvas.getContext) {   
   var ctx = canvas.getContext('2d');   
   // drawing code here   
} else {   
   
   // canvas-unsupported code here 
}  

Browser Support

The latest versions of Firefox, Safari, Chrome and Opera all support for HTML5 Canvas but IE8 does not support canvas natively.

You can use ExplorerCanvas to have canvas support through Internet Explorer. You just need to include this JavaScript as follows −

<!--[if IE]><script src = "excanvas.js"></script><![endif]-->

HTML5 Canvas Examples

This tutorial covers the following examples related to HTML5 <canvas> element.

Sr.No. Examples & Description
1 Drawing Rectangles

Learn how to draw rectangle using HTML5 <canvas> element

2 Drawing Paths

Learn how to make shapes using paths in HTML5 <canvas> element

3 Drawing Lines

Learn how to draw lines using HTML5 <canvas> element

4 Drawing Bezier

Learn how to draw Bezier curve using HTML5 <canvas> element

5 Drawing Quadratic

Learn how to draw quadratic curve using HTML5 <canvas> element

6 Using Images

Learn how to use images with HTML5 <canvas> element

7 Create Gradients

Learn how to create gradients using HTML5 <canvas> element

8 Styles and Colors

Learn how to apply styles and colors using HTML5 <canvas> element

9 Text and Fonts

Learn how to draw amazing text using different fonts and their size.

10 Pattern and Shadow

Learn how to draw different patterns and drop shadows.

11 Canvas States

Learn how to save and restore canvas states while doing complex drawings on a canvas.

12 Canvas Translation

This method is used to move the canvas and its origin to a different point in the grid.

13 Canvas Rotation

This method is used to rotate the canvas around the current origin.

14 Canvas Scaling

This method is used to increase or decrease the units in a canvas grid.

15 Canvas Transform

These methods allow modifications directly to the transformation matrix.

16 Canvas Composition

This method is used to mask off certain areas or clear sections from the canvas.

17 Canvas Animation

Learn how to create basic animation using HTML5 canvas and JavaScript.

HTML5 - Audio & Video

HTML5 features include native audio and video support without the need for Flash.

The HTML5 <audio> and <video> tags make it simple to add media to a website. You need to set src attribute to identify the media source and include a controls attribute so the user can play and pause the media.

Embedding Video

Here is the simplest form of embedding a video file in your webpage −

<video src = "foo.mp4"  width = "300" height = "200" controls>
   Your browser does not support the <video> element.   
</video>

The current HTML5 draft specification does not specify which video formats browsers should support in the video tag. But most commonly used video formats are −

  • Ogg − Ogg files with Thedora video codec and Vorbis audio codec.

  • mpeg4 − MPEG4 files with H.264 video codec and AAC audio codec.

You can use <source> tag to specify media along with media type and many other attributes. A video element allows multiple source elements and browser will use the first recognized format −

Live Demo

<!DOCTYPE HTML>

<html>
   <body>
      
      <video  width = "300" height = "200" controls autoplay>
         <source src = "/html5/foo.ogg" type ="video/ogg" />
         <source src = "/html5/foo.mp4" type = "video/mp4" />
         Your browser does not support the <video> element.
      </video>
      
   </body>
</html>

This will produce the following result −

Video Attribute Specification

The HTML5 video tag can have a number of attributes to control the look and feel and various functionalities of the control −

Sr.No. Attribute & Description
1

autoplay

This Boolean attribute if specified, the video will automatically begin to play back as soon as it can do so without stopping to finish loading the data.

2

autobuffer

This Boolean attribute if specified, the video will automatically begin buffering even if it's not set to automatically play.

3

controls

If this attribute is present, it will allow the user to control video playback, including volume, seeking, and pause/resume playback.

4

height

This attribute specifies the height of the video's display area, in CSS pixels.

5

loop

This Boolean attribute if specified, will allow video automatically seek back to the start after reaching at the end.

6

preload

This attribute specifies that the video will be loaded at page load, and ready to run. Ignored if autoplay is present.

7

poster

This is a URL of an image to show until the user plays or seeks.

8

src

The URL of the video to embed. This is optional; you may instead use the <source> element within the video block to specify the video to embed.

9

width

This attribute specifies the width of the video's display area, in CSS pixels.

Embedding Audio

HTML5 supports <audio> tag which is used to embed sound content in an HTML or XHTML document as follows.

<audio src = "foo.wav" controls autoplay>
   Your browser does not support the <audio> element.   
</audio>

The current HTML5 draft specification does not specify which audio formats browsers should support in the audio tag. But most commonly used audio formats are ogg, mp3 and wav.

You can use <source&ggt; tag to specify media along with media type and many other attributes. An audio element allows multiple source elements and browser will use the first recognized format −

Live Demo

<!DOCTYPE HTML>

<html>
   <body>
      
      <audio controls autoplay>
         <source src = "/html5/audio.ogg" type = "audio/ogg" />
         <source src = "/html5/audio.wav" type = "audio/wav" />
         Your browser does not support the <audio> element.
      </audio>
      
   </body>
</html>

This will produce the following result −

Audio Attribute Specification

The HTML5 audio tag can have a number of attributes to control the look and feel and various functionalities of the control −

Sr.No. Attribute & Description
1

autoplay

This Boolean attribute if specified, the audio will automatically begin to play back as soon as it can do so without stopping to finish loading the data.

2

autobuffer

This Boolean attribute if specified, the audio will automatically begin buffering even if it's not set to automatically play.

3

controls

If this attribute is present, it will allow the user to control audio playback, including volume, seeking, and pause/resume playback.

4

loop

This Boolean attribute if specified, will allow audio automatically seek back to the start after reaching at the end.

5

preload

This attribute specifies that the audio will be loaded at page load, and ready to run. Ignored if autoplay is present.

6

src

The URL of the audio to embed. This is optional; you may instead use the <source> element within the video block to specify the video to embed.

Handling Media Events

The HTML5 audio and video tag can have a number of attributes to control various functionalities of the control using JavaScript −

S.No. Event & Description
1

abort

This event is generated when playback is aborted.

2

canplay

This event is generated when enough data is available that the media can be played.

3

ended

This event is generated when playback completes.

4

error

This event is generated when an error occurs.

5

loadeddata

This event is generated when the first frame of the media has finished loading.

6

loadstart

This event is generated when loading of the media begins.

7

pause

This event is generated when playback is paused.

8

play

This event is generated when playback starts or resumes.

9

progress

This event is generated periodically to inform the progress of the downloading the media.

10

ratechange

This event is generated when the playback speed changes.

11

seeked

This event is generated when a seek operation completes.

12

seeking

This event is generated when a seek operation begins.

13

suspend

This event is generated when loading of the media is suspended.

14

volumechange

This event is generated when the audio volume changes.

15

waiting

This event is generated when the requested operation (such as playback) is delayed pending the completion of another operation (such as a seek).

Following is the example which allows to play the given video −

Live Demo

<!DOCTYPE HTML>

<html>
   <head>
   
      <script type = "text/javascript">
         function PlayVideo() {
            var v = document.getElementsByTagName("video")[0];  
            v.play(); 
         }
      </script>
   </head>
   
   <body>
   
      <form>         
         <video width = "300" height = "200" src = "/html5/foo.mp4">
         Your browser does not support the video element.
         </video>
         <br />
         <input type = "button" onclick = "PlayVideo();" value = "Play"/>
      </form>
      
   </body>
</html>

This will produce the following result −

Configuring Servers for Media Type

Most servers don't by default serve Ogg or mp4 media with the correct MIME types, so you'll likely need to add the appropriate configuration for this.

AddType audio/ogg .oga
AddType audio/wav .wav
AddType video/ogg .ogv .ogg
AddType video/mp4 .mp4

HTML5 - Geolocation

HTML5 Geolocation API lets you share your location with your favorite web sites. A JavaScript can capture your latitude and longitude and can be sent to backend web server and do fancy location-aware things like finding local businesses or showing your location on a map.

Today most of the browsers and mobile devices support Geolocation API. The geolocation APIs work with a new property of the global navigator object ie. Geolocation object which can be created as follows −

var geolocation = navigator.geolocation;

The geolocation object is a service object that allows widgets to retrieve information about the geographic location of the device.

Geolocation Methods

The geolocation object provides the following methods −

Sr.No. Method & Description
1 getCurrentPosition()

This method retrieves the current geographic location of the user.

2 watchPosition()

This method retrieves periodic updates about the current geographic location of the device.

3 clearWatch()

This method cancels an ongoing watchPosition call.

Example

Following is a sample code to use any of the above method −

function getLocation() {
   var geolocation = navigator.geolocation;
   geolocation.getCurrentPosition(showLocation, errorHandler);
}

Here showLocation and errorHandler are callback methods which would be used to get actual position as explained in next section and to handle errors if there is any.

Location Properties

Geolocation methods getCurrentPosition() and getPositionUsingMethodName() specify the callback method that retrieves the location information. These methods are called asynchronously with an object Position which stores the complete location information.

The Position object specifies the current geographic location of the device. The location is expressed as a set of geographic coordinates together with information about heading and speed.

The following table describes the properties of the Position object. For the optional properties if the system cannot provide a value, the value of the property is set to null.

Property Type Description
coords objects Specifies the geographic location of the device. The location is expressed as a set of geographic coordinates together with information about heading and speed.
coords.latitude Number Specifies the latitude estimate in decimal degrees. The value range is [-90.00, +90.00].
coords.longitude Number Specifies the longitude estimate in decimal degrees. The value range is [-180.00, +180.00].
coords.altitude Number [Optional] Specifies the altitude estimate in meters above the WGS 84 ellipsoid.
coords.accuracy Number [Optional] Specifies the accuracy of the latitude and longitude estimates in meters.
coords.altitudeAccuracy Number [Optional] Specifies the accuracy of the altitude estimate in meters.
coords.heading Number [Optional] Specifies the device's current direction of movement in degrees counting clockwise relative to true north.
coords.speed Number [Optional] Specifies the device's current ground speed in meters per second.
timestamp date Specifies the time when the location information was retrieved and the Position object created.

Example

Following is a sample code which makes use of Position object. Here showLocation method is a callback method −

function showLocation( position ) {
   var latitude = position.coords.latitude;
   var longitude = position.coords.longitude;
   ...
}

Handling Errors

Geolocation is complicated, and it is very much required to catch any error and handle it gracefully.

The geolocations methods getCurrentPosition() and watchPosition() make use of an error handler callback method which gives PositionError object. This object has following two properties −

Property Type Description
code Number Contains a numeric code for the error.
message String Contains a human-readable description of the error.

The following table describes the possible error codes returned in the PositionError object.

Code Constant Description
0 UNKNOWN_ERROR The method failed to retrieve the location of the device due to an unknown error.
1 PERMISSION_DENIED The method failed to retrieve the location of the device because the application does not have permission to use the Location Service.
2 POSITION_UNAVAILABLE The location of the device could not be determined.
3 TIMEOUT The method was unable to retrieve the location information within the specified maximum timeout interval.

Example

Following is a sample code which makes use of PositionError object. Here errorHandler method is a callback method −

function errorHandler( err ) {
   
   if (err.code == 1) {
      
      // access is denied
   }
   ...
}

Position Options

Following is the actual syntax of getCurrentPosition() method −

getCurrentPosition(callback, ErrorCallback, options)

Here third argument is the PositionOptions object which specifies a set of options for retrieving the geographic location of the device.

Following are the options which can be specified as third argument −

Property Type Description
enableHighAccuracy Boolean Specifies whether the widget wants to receive the most accurate location estimate possible. By default this is false.
timeout Number The timeout property is the number of milliseconds your web application is willing to wait for a position.
maximumAge Number Specifies the expiry time in milliseconds for cached location information.

Example

Following is a sample code which shows how to use above mentioned methods −

function getLocation() {
   var geolocation = navigator.geolocation;
   geolocation.getCurrentPosition(showLocation, errorHandler, {maximumAge: 75000});
}

HTML5 - Microdata

Microdata is a standardized way to provide additional semantics in your web pages.

Microdata lets you define your own customized elements and start embedding custom properties in your web pages. At a high level, microdata consists of a group of name-value pairs.

The groups are called items, and each name-value pair is a property. Items and properties are represented by regular elements.

Example

  • To create an item, the itemscope attribute is used.

  • To add a property to an item, the itemprop attribute is used on one of the item's descendants.

Here there are two items, each of which has the property "name" −

Live Demo

<html>
   <body>
      
      <div itemscope>
         <p>My name is <span itemprop = "name">Zara</span>.</p>
      </div>
      
      <div itemscope>
         <p>My name is <span itemprop = "name">Nuha</span>.</p>
      </div>
      
   </body>
</html>

It will produce the following result −

Properties generally have values that are strings but it can have following data types −

Global Attributes

Microdata introduces five global attributes which would be available for any element to use and give context for machines about your data.

Sr.No. Attribute & Description
1

itemscope

This is used to create an item. The itemscope attribute is a Boolean attribute that tells that there is Microdata on this page, and this is where it starts.

2

itemtype

This attribute is a valid URL which defines the item and provides the context for the properties.

3

itemid

This attribute is global identifier for the item.

4

itemprop

This attribute defines a property of the item.

5

itemref

This attribute gives a list of additional elements to crawl to find the name-value pairs of the item.

Properties Datatypes

Properties generally have values that are strings as mentioned in above example but they can also have values that are URLs. Following example has one property, "image", whose value is a URL −

<div itemscope>
   <img itemprop = "image" src = "tp-logo.gif" alt = "TutorialsPoint">
</div>

Properties can also have values that are dates, times, or dates and times. This is achieved using the time element and its datetime attribute.

Live Demo

<html>
   <body>
      
      <div itemscope>
         My birthday is:
         <time itemprop = "birthday" datetime = "1971-05-08">
            Aug 5th 1971
         </time>
      </div>
      
   </body>
</html>

It will produce the following result −

Properties can also themselves be groups of name-value pairs, by putting the itemscope attribute on the element that declares the property.

Microdata API support

If a browser supports the HTML5 microdata API, there will be a getItems() function on the global document object. If browser doesn't support microdata, the getItems() function will be undefined.

function supports_microdata_api() {
   return !!document.getItems;
}

Modernizr does not yet support checking for the microdata API, so you’ll need to use the function like the one listed above.

The HTML5 microdata standard includes both HTML markup (primarily for search engines) and a set of DOM functions (primarily for browsers).

You can include microdata markup in your web pages, and search engines that don't understand the microdata attributes will just ignore them. But if you need to access or manipulate microdata through the DOM, you'll need to check whether the browser supports the microdata DOM API.

Defining Microdata Vocabulary

To define microdata vocabulary you need a namespace URL which points to a working web page. For example https://data-vocabulary.org/Person can be used as the namespace for a personal microdata vocabulary with the following named properties −

  • name − Person name as a simple string

  • Photo − A URL to a picture of the person.

  • URL − A website belonging to the person.

Using about properties a person microdata could be as follows −

Live Demo

<html>
   <body>
   
      <div itemscope>
         <section itemscope itemtype = "http://data-vocabulary.org/Person">
            <h1 itemprop = "name">Gopal K Varma</h1>
         
            <p>
               <img itemprop = "photo" 
                  src = "http://www.tutorialspoint.com/green/images/logo.png">
            </p>
            
            <a itemprop = "url" href = "#">Site</a>
         </section>
      </div>
      
   </body>
</html>

It will produce the following result −

Google supports microdata as part of their Rich Snippets program. When Google's web crawler parses your page and finds microdata properties that conform to the http://datavocabulary.org/Person vocabulary, it parses out those properties and stores them alongside the rest of the page data.

You can test above example using Rich Snippets Testing Tool using http://www.tutorialspoint.com/html5/microdata.htm

For further development on Microdata you can always refer to HTML5 Microdata.

HTML5 - Drag & drop

Drag and Drop (DnD) is powerful User Interface concept which makes it easy to copy, reorder and deletion of items with the help of mouse clicks. This allows the user to click and hold the mouse button down over an element, drag it to another location, and release the mouse button to drop the element there.

To achieve drag and drop functionality with traditional HTML4, developers would either have to either have to use complex JavaScript programming or other JavaScript frameworks like jQuery etc.

Now HTML 5 came up with a Drag and Drop (DnD) API that brings native DnD support to the browser making it much easier to code up.

HTML 5 DnD is supported by all the major browsers like Chrome, Firefox 3.5 and Safari 4 etc.

Drag and Drop Events

There are number of events which are fired during various stages of the drag and drop operation. These events are listed below −

Sr.No. Events & Description
1

dragstart

Fires when the user starts dragging of the object.

2

dragenter

Fired when the mouse is first moved over the target element while a drag is occurring. A listener for this event should indicate whether a drop is allowed over this location. If there are no listeners, or the listeners perform no operations, then a drop is not allowed by default.

3

dragover

This event is fired as the mouse is moved over an element when a drag is occurring. Much of the time, the operation that occurs during a listener will be the same as the dragenter event.

4

dragleave

This event is fired when the mouse leaves an element while a drag is occurring. Listeners should remove any highlighting or insertion markers used for drop feedback.

5

drag

Fires every time the mouse is moved while the object is being dragged.

6

drop

The drop event is fired on the element where the drop was occurred at the end of the drag operation. A listener would be responsible for retrieving the data being dragged and inserting it at the drop location.

7

dragend

Fires when the user releases the mouse button while dragging an object.

Note − Note that only drag events are fired; mouse events such as mousemove are not fired during a drag operation.

The DataTransfer Object

The event listener methods for all the drag and drop events accept Event object which has a readonly attribute called dataTransfer.

The event.dataTransfer returns DataTransfer object associated with the event as follows −

function EnterHandler(event) {
   DataTransfer dt = event.dataTransfer;
   .............
}

The DataTransfer object holds data about the drag and drop operation. This data can be retrieved and set in terms of various attributes associated with DataTransfer object as explained below −

Sr.No. DataTransfer attributes and their description
1

dataTransfer.dropEffect [ = value ]

  • Returns the kind of operation that is currently selected.

  • This attribute can be set, to change the selected operation.

  • The possible values are none, copy, link, and move.

2

dataTransfer.effectAllowed [ = value ]

  • Returns the kinds of operations that are to be allowed.

  • This attribute can be set, to change the allowed operations.

  • The possible values are none, copy, copyLink, copyMove, link, linkMove, move, all and uninitialized.

3

dataTransfer.types

Returns a DOMStringList listing the formats that were set in the dragstart event. In addition, if any files are being dragged, then one of the types will be the string "Files".

4

dataTransfer.clearData ( [ format ] )

Removes the data of the specified formats. Removes all data if the argument is omitted.

5

dataTransfer.setData(format, data)

Adds the specified data.

6

data = dataTransfer.getData(format)

Returns the specified data. If there is no such data, returns the empty string.

7

dataTransfer.files

Returns a FileList of the files being dragged, if any.

8

dataTransfer.setDragImage(element, x, y)

Uses the given element to update the drag feedback, replacing any previously specified feedback.

9

dataTransfer.addElement(element)

Adds the given element to the list of elements used to render the drag feedback.

Drag and Drop Process

Following are the steps to be carried out to implement Drag and Drop operation −

Step 1 - Making an Object Draggable

Here are steps to be taken −

  • If you want to drag an element, you need to set the draggable attribute to true for that element.

  • Set an event listener for dragstart that stores the data being dragged.

  • The event listener dragstart will set the allowed effects (copy, move, link, or some combination).

Following is the example to make an object draggable −

Live Demo

<!DOCTYPE HTML>

<html>
   <head>
      
      <style type = "text/css">
         
         #boxA, #boxB {
            float:left;padding:10px;margin:10px; -moz-user-select:none;
         }
         #boxA { background-color: #6633FF; width:75px; height:75px;  }
         #boxB { background-color: #FF6699; width:150px; height:150px; }
      </style>
      
      <script type = "text/javascript">
         
         function dragStart(ev) {
            ev.dataTransfer.effectAllowed = 'move';
            ev.dataTransfer.setData("Text", ev.target.getAttribute('id'));
            ev.dataTransfer.setDragImage(ev.target,0,0);
            
            return true;
         }
      </script>
      
   </head>
   <body>
      
      <center>
         <h2>Drag and drop HTML5 demo</h2>
         <div>Try to drag the purple box around.</div>
         
         <div id = "boxA" draggable = "true" 
            ondragstart = "return dragStart(ev)">
            <p>Drag Me</p>
         </div>
         
         <div id = "boxB">Dustbin</div>
      </center>
      
   </body>
</html>

This will produce the following result −

Step 2 - Dropping the Object

To accept a drop, the drop target has to listen to at least three events.

  • The dragenter event, which is used to determine whether or not the drop target is to accept the drop. If the drop is to be accepted, then this event has to be canceled.

  • The dragover event, which is used to determine what feedback is to be shown to the user. If the event is canceled, then the feedback (typically the cursor) is updated based on the dropEffect attribute's value.

  • Finally, the drop event, which allows the actual drop to be performed.

Following is the example to drop an object into another object −

Live Demo

<html>
   <head>
      <style type="text/css">
         #boxA, #boxB {
            float:left;padding:10px;margin:10px;-moz-user-select:none;
         }
         #boxA { background-color: #6633FF; width:75px; height:75px;  }
         #boxB { background-color: #FF6699; width:150px; height:150px; }
      </style>
      <script type="text/javascript">
         function dragStart(ev) {
            ev.dataTransfer.effectAllowed='move';
            ev.dataTransfer.setData("Text", ev.target.getAttribute('id'));
            ev.dataTransfer.setDragImage(ev.target,0,0);
            return true;
         }
         function dragEnter(ev) {
            event.preventDefault();
            return true;
         }
         function dragOver(ev) {
            return false;
         }
         function dragDrop(ev) {
            var src = ev.dataTransfer.getData("Text");
            ev.target.appendChild(document.getElementById(src));
            ev.stopPropagation();
            return false;
         }
      </script>
   </head>
   <body>
      <center>
         <h2>Drag and drop HTML5 demo</h2>
         <div>Try to move the purple box into the pink box.</div>
         <div id="boxA" draggable="true" ondragstart="return dragStart(event)">
            <p>Drag Me</p>
         </div>
         <div id="boxB" ondragenter="return dragEnter(event)" ondrop="return dragDrop(event)" ondragover="return dragOver(event)">Dustbin</div>
      </center>
   </body>
</html>

This will produce the following result −

HTML5 - Web Workers

JavaScript was designed to run in a single-threaded environment, meaning multiple scripts cannot run at the same time. Consider a situation where you need to handle UI events, query and process large amounts of API data, and manipulate the DOM.

JavaScript will hang your browser in situation where CPU utilization is high. Let us take a simple example where JavaScript goes through a big loop −

Live Demo

<!DOCTYPE HTML>

<html>
   <head>
      <title>Big for loop</title>
      
      <script>
         function bigLoop() {
            
            for (var i = 0; i <= 10000; i += 1) {
               var j = i;
            }
            alert("Completed " + j + "iterations" );
         }
         
         function sayHello(){
            alert("Hello sir...." );
         }
      </script>
      
   </head>
   
   <body>
      <input type = "button" onclick = "bigLoop();" value = "Big Loop" />
      <input type = "button" onclick = "sayHello();" value = "Say Hello" />
   </body>
</html>

It will produce the following result −

When you click Big Loop button it displays following result in Firefox −

Big Loop

What is Web Workers?

The situation explained above can be handled using Web Workers who will do all the computationally expensive tasks without interrupting the user interface and typically run on separate threads.

Web Workers allow for long-running scripts that are not interrupted by scripts that respond to clicks or other user interactions, and allows long tasks to be executed without yielding to keep the page responsive.

Web Workers are background scripts and they are relatively heavy-weight, and are not intended to be used in large numbers. For example, it would be inappropriate to launch one worker for each pixel of a four megapixel image.

When a script is executing inside a Web Worker it cannot access the web page's window object (window.document), which means that Web Workers don't have direct access to the web page and the DOM API. Although Web Workers cannot block the browser UI, they can still consume CPU cycles and make the system less responsive.

How Web Workers Work?

Web Workers are initialized with the URL of a JavaScript file, which contains the code the worker will execute. This code sets event listeners and communicates with the script that spawned it from the main page. Following is the simple syntax −

var worker = new Worker('bigLoop.js');

If the specified javascript file exists, the browser will spawn a new worker thread, which is downloaded asynchronously. If the path to your worker returns an 404 error, the worker will fail silently.

If your application has multiple supporting JavaScript files, you can import them importScripts() method which takes file name(s) as argument separated by comma as follows −

importScripts("helper.js", "anotherHelper.js");

Once the Web Worker is spawned, communication between web worker and its parent page is done using the postMessage() method. Depending on your browser/version, postMessage() can accept either a string or JSON object as its single argument.

Message passed by Web Worker is accessed using onmessage event in the main page. Now let us write our bigLoop example using Web Worker. Below is the main page (hello.htm) which will spawn a web worker to execute the loop and to return the final value of variablej

Live Demo

<!DOCTYPE HTML>

<html>
   <head>
      <title>Big for loop</title>
      
      <script>
         var worker = new Worker('bigLoop.js');
         
         worker.onmessage = function (event) {
            alert("Completed " + event.data + "iterations" );
         };
         
         function sayHello() {
            alert("Hello sir...." );
         }
      </script>
   </head>
   
   <body>
      <input type = "button" onclick = "sayHello();" value = "Say Hello"/>
   </body>
</html>

Following is the content of bigLoop.js file. This makes use of postMessage() API to pass the communication back to main page −

for (var i = 0; i <= 1000000000; i += 1) {
   var j = i;
}
postMessage(j);

This will produce the following result −

Stopping Web Workers

Web Workers don't stop by themselves but the page that started them can stop them by calling terminate() method.

worker.terminate();

A terminated Web Worker will no longer respond to messages or perform any additional computations. You cannot restart a worker; instead, you can create a new worker using the same URL.

Handling Errors

The following shows an example of an error handling function in a Web Worker JavaScript file that logs errors to the console. With error handling code, above example would become as following −

<!DOCTYPE HTML>

<html>
   <head>
      <title>Big for loop</title>
      
      <script>
         var worker = new Worker('bigLoop.js');
         
         worker.onmessage = function (event) {
            alert("Completed " + event.data + "iterations" );
         };
         
         worker.onerror = function (event) {
            console.log(event.message, event);
         };
         
         function sayHello() {
            alert("Hello sir...." );
         }
      </script>
   </head>
   
   <body>
      <input type = "button" onclick = "sayHello();" value = "Say Hello"/>
   </body>
</html>

Checking for Browser Support

Following is the syntax to detect a Web Worker feature support available in a browser −

Live Demo

<!DOCTYPE HTML>

<html>
   <head>
      <title>Big for loop</title>
      <script src = "/js/modernizr-1.5.min.js"></script>
      
      <script>
      function myFunction() {
         
         if (Modernizr.webworkers) {
            alert("Congratulation!! you have web workers support." );
         } else {
            alert("Sorry!! you do not have web workers support." );
         }
      }
      </script>
   </head>
   
   <body>
      <button onclick = "myFunction()">Click me</button>
   </body>
</html>

This will produce the following result −

HTML5 - IndexedDB

The indexeddb is a new HTML5 concept to store the data inside user's browser. indexeddb is more power than local storage and useful for applications that requires to store large amount of the data. These applications can run more efficiency and load faster.

Why to use indexeddb?

The W3C has announced that the Web SQL database is a deprecated local storage specification so web developer should not use this technology any more. indexeddb is an alternative for web SQL data base and more effective than older technologies.

Features

  • it stores key-pair values
  • it is not a relational database
  • IndexedDB API is mostly asynchronous
  • it is not a structured query language
  • it has supported to access the data from same domain

IndexedDB

Before enter into an indexeddb, we need to add some prefixes of implementation as shown below

window.indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || 
window.msIndexedDB;
 
window.IDBTransaction = window.IDBTransaction || window.webkitIDBTransaction || 
window.msIDBTransaction;
window.IDBKeyRange = window.IDBKeyRange || 
window.webkitIDBKeyRange || window.msIDBKeyRange
 
if (!window.indexedDB) {
   window.alert("Your browser doesn't support a stable version of IndexedDB.")
}

Open an IndexedDB database

Before creating a database, we have to prepare some data for the data base.let's start with company employee details.

const employeeData = [
   { id: "01", name: "Gopal K Varma", age: 35, email: "contact@tutorialspoint.com" },
   { id: "02", name: "Prasad", age: 24, email: "prasad@tutorialspoint.com" }
];

Adding the data

Here adding some data manually into the data as shown below −

function add() {
   var request = db.transaction(["employee"], "readwrite")
   .objectStore("employee")
   .add({ id: "01", name: "prasad", age: 24, email: "prasad@tutorialspoint.com" });
   
   request.onsuccess = function(event) {
      alert("Prasad has been added to your database.");
   };
   
   request.onerror = function(event) {
      alert("Unable to add data
Prasad is already exist in your database! ");
   }
}

Retrieving Data

We can retrieve the data from the data base using with get()

function read() {
   var transaction = db.transaction(["employee"]);
   var objectStore = transaction.objectStore("employee");
   var request = objectStore.get("00-03");
   
   request.onerror = function(event) {
      alert("Unable to retrieve daa from database!");
   };
   
   request.onsuccess = function(event) {
      
      if(request.result) {
         alert("Name: " + request.result.name + ", Age: 
            " + request.result.age + ", Email: " + request.result.email);
      } else {
         alert("Kenny couldn't be found in your database!");  
      }
   };
}

Using with get(), we can store the data in object instead of that we can store the data in cursor and we can retrieve the data from cursor.

function readAll() {
   var objectStore = db.transaction("employee").objectStore("employee");
   
   objectStore.openCursor().onsuccess = function(event) {
      var cursor = event.target.result;
      
      if (cursor) {
         alert("Name for id " + cursor.key + " is " + cursor.value.name + ", 
            Age: " + cursor.value.age + ", Email: " + cursor.value.email);
         cursor.continue();
      } else {
         alert("No more entries!");
      }
   };
}

Removing the data

We can remove the data from IndexedDB with remove().Here is how the code looks like

function remove() {
   var request = db.transaction(["employee"], "readwrite")
   .objectStore("employee")
   .delete("02");
   
   request.onsuccess = function(event) {
      alert("prasad entry has been removed from your database.");
   };
}

HTML Code

To show all the data we need to use onClick event as shown below code −

<!DOCTYPE html>

<html>
   <head>
      <meta http-equiv = "Content-Type" content = "text/html; charset = utf-8" />
      <title>IndexedDb Demo | onlyWebPro.com</title>
   </head>
   
   <body>
      <button onclick = "read()">Read </button>
      <button onclick = "readAll()"></button>
      <button onclick = "add()"></button>
      <button onclick = "remove()">Delete </button>
   </body>
</html>

The final code should be as −

<!DOCTYPE html>

<html>
   <head>
      <meta http-equiv = "Content-Type" content = "text/html; charset = utf-8" />
      <script type = "text/javascript">
         
         //prefixes of implementation that we want to test
         window.indexedDB = window.indexedDB || window.mozIndexedDB || 
         window.webkitIndexedDB || window.msIndexedDB;
         
         //prefixes of window.IDB objects
         window.IDBTransaction = window.IDBTransaction || 
         window.webkitIDBTransaction || window.msIDBTransaction;
         window.IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange || 
         window.msIDBKeyRange
         
         if (!window.indexedDB) {
            window.alert("Your browser doesn't support a stable version of IndexedDB.")
         }
         
         const employeeData = [
            { id: "00-01", name: "gopal", age: 35, email: "gopal@tutorialspoint.com" },
            { id: "00-02", name: "prasad", age: 32, email: "prasad@tutorialspoint.com" }
         ];
         var db;
         var request = window.indexedDB.open("newDatabase", 1);
         
         request.onerror = function(event) {
            console.log("error: ");
         };
         
         request.onsuccess = function(event) {
            db = request.result;
            console.log("success: "+ db);
         };
         
         request.onupgradeneeded = function(event) {
            var db = event.target.result;
            var objectStore = db.createObjectStore("employee", {keyPath: "id"});
            
            for (var i in employeeData) {
               objectStore.add(employeeData[i]);
            }
         }
         
         function read() {
            var transaction = db.transaction(["employee"]);
            var objectStore = transaction.objectStore("employee");
            var request = objectStore.get("00-03");
            
            request.onerror = function(event) {
               alert("Unable to retrieve daa from database!");
            };
            
            request.onsuccess = function(event) {
               // Do something with the request.result!
               if(request.result) {
                  alert("Name: " + request.result.name + ", 
                     Age: " + request.result.age + ", Email: " + request.result.email);
               } else {
                  alert("Kenny couldn't be found in your database!");
               }
            };
         }
         
         function readAll() {
            var objectStore = db.transaction("employee").objectStore("employee");
            
            objectStore.openCursor().onsuccess = function(event) {
               var cursor = event.target.result;
               
               if (cursor) {
                  alert("Name for id " + cursor.key + " is " + cursor.value.name + ", 
                     Age: " + cursor.value.age + ", Email: " + cursor.value.email);
                  cursor.continue();
               } else {
                  alert("No more entries!");
               }
            };
         }
         
         function add() {
            var request = db.transaction(["employee"], "readwrite")
            .objectStore("employee")
            .add({ id: "00-03", name: "Kenny", age: 19, email: "kenny@planet.org" });
            
            request.onsuccess = function(event) {
               alert("Kenny has been added to your database.");
            };
            
            request.onerror = function(event) {
               alert("Unable to add data
Kenny is aready exist in your database! ");
            }
         }
         
         function remove() {
            var request = db.transaction(["employee"], "readwrite")
            .objectStore("employee")
            .delete("00-03");
            
            request.onsuccess = function(event) {
               alert("Kenny's entry has been removed from your database.");
            };
         }
      </script>
      
   </head>
   <body>
      <button onclick = "read()">Read </button>
      <button onclick = "readAll()">Read all </button>
      <button onclick = "add()">Add data </button>
      <button onclick = "remove()">Delete data </button>
   </body>
</html>

It will produce the following output −

HTML5 - Web messaging

Web messaging is the ability to send realtime messages from the server to the client browser. It overrides the cross domain communication problem in different domains, protocols or ports

For example, you want to send the data from your page to ad container which is placed at iframe or voice-versa, in this scenario, Browser throws a security exception. With web messaging we can pass the data across as a message event.

Message Event

Message events fires Cross-document messaging, channel messaging, server-sent events and web sockets.it has described by Message Event interface.

Attributes

Sr.No. Attributes & Description
1

data

Contains string data

2

origin

Contains Domain name and port

3

lastEventId

Contains unique identifier for the current message event.

4

source

Contains to A reference to the originating document’s window

5

ports

Contains the data which is sent by any message port

Sending a cross-document message

Before send cross document message, we need to create a new web browsing context either by creating new iframe or new window. We can send the data using with postMessage() and it has two arguments. They are as −

  • message − The message to send
  • targetOrigin − Origin name

Examples

Sending message from iframe to button

var iframe = document.querySelector('iframe');
var button = document.querySelector('button');

var clickHandler = function() {
   iframe.contentWindow.postMessage('The message to send.',
      'https://www.tutorialspoint.com);
}
button.addEventListener('click',clickHandler,false);

Receiving a cross-document message in the receiving document

var messageEventHandler = function(event){
   
   // check that the origin is one we want.
   if(event.origin == 'https://www.tutorialspoint.com') {
      alert(event.data);
   }
}
window.addEventListener('message', messageEventHandler,false);

Channel messaging

Two-way communication between the browsing contexts is called channel messaging. It is useful for communication across multiple origins.

The MessageChannel and MessagePort Objects

While creating messageChannel, it internally creates two ports to sending the data and forwarded to another browsing context.

  • postMessage() − Post the message throw channel

  • start() − It sends the data

  • close() − It close the ports

In this scenario, we are sending the data from one iframe to another iframe. Here we are invoking the data in function and passing the data to DOM.

var loadHandler = function() {
   var mc, portMessageHandler;
   mc = new MessageChannel();
   window.parent.postMessage('documentAHasLoaded','http://foo.example',[mc.port2]);
   
   portMessageHandler = function(portMsgEvent) {
      alert( portMsgEvent.data );
   }
   
   mc.port1.addEventListener('message', portMessageHandler, false);
   mc.port1.start();
}
window.addEventListener('DOMContentLoaded', loadHandler, false);

Above code, it is taking the data from port 2, now it will pass the data to second iframe

var loadHandler = function() {
   var iframes, messageHandler;
   iframes = window.frames;
   
   messageHandler = function(messageEvent) {
      
      if( messageEvent.ports.length > 0 ) {
         
         // transfer the port to iframe[1]
         iframes[1].postMessage('portopen','http://foo.example',messageEvent.ports);
      }
   }
   window.addEventListener('message',messageHandler,false);
}
window.addEventListener('DOMContentLoaded',loadHandler,false);

Now second document handles the data by using the portMsgHandler function.

var loadHandler() {
   
   // Define our message handler function
   var messageHandler = function(messageEvent) {
   
      // Our form submission handler
      
      var formHandler = function() {
         var msg = 'add <foo@example.com> to game circle.';
         messageEvent.ports[0].postMessage(msg);
      }
      document.forms[0].addEventListener('submit',formHandler,false);
   }
   window.addEventListener('message',messageHandler,false);
}
window.addEventListener('DOMContentLoaded',loadHandler,false);

HTML5 - CORS

Cross-origin resource sharing (CORS) is a mechanism to allows the restricted resources from another domain in web browser.

For suppose, if you click on HTML5- video player in html5 demo sections. it will ask camera permission. if user allow the permission then only it will open the camera or else it doesn't open the camera for web applications.

Making a CORS request

Here Chrome, Firefox, Opera and Safari all use the XMLHttprequest2 object and Internet Explorer uses the similar XDomainRequest object, object.

function createCORSRequest(method, url) {
   var xhr = new XMLHttpRequest();
   
   if ("withCredentials" in xhr) {
      
      // Check if the XMLHttpRequest object has a "withCredentials" property.
      // "withCredentials" only exists on XMLHTTPRequest2 objects.
      xhr.open(method, url, true);
   } else if (typeof XDomainRequest != "undefined") {
      
      // Otherwise, check if XDomainRequest.
      // XDomainRequest only exists in IE, and is IE's way of making CORS requests.
      xhr = new XDomainRequest();
      xhr.open(method, url);
   } else {
      
      // Otherwise, CORS is not supported by the browser.
      xhr = null;
   }
   return xhr;
}

var xhr = createCORSRequest('GET', url);

if (!xhr) {
   throw new Error('CORS not supported');
}

Event handles in CORS

Sr.No. Event Handler & Description
1

onloadstart

Starts the request

2

onprogress

Loads the data and send the data

3

onabort

Abort the request

4

onerror

request has failed

5

onload

request load successfully

6

ontimeout

time out has happened before request could complete

7

onloadend

When the request is complete either successful or failure

Example of onload or onerror event

xhr.onload = function() {
   var responseText = xhr.responseText;
   
   // process the response.
   console.log(responseText);
};

xhr.onerror = function() {
   console.log('There was an error!');
};

Example of CORS with handler

Below example will show the example of makeCorsRequest() and onload handler

// Create the XHR object.
function createCORSRequest(method, url) {
   var xhr = new XMLHttpRequest();
   
   if ("withCredentials" in xhr) {
      
      // XHR for Chrome/Firefox/Opera/Safari.
      xhr.open(method, url, true);
   } else if (typeof XDomainRequest != "undefined") {
      
      // XDomainRequest for IE.
      xhr = new XDomainRequest();
      xhr.open(method, url);
   } else {
      
      // CORS not supported.
      xhr = null;
   }
   return xhr;
}

// Helper method to parse the title tag from the response.
function getTitle(text) {
   return text.match('<title>(.*)?</title>')[1];
}

// Make the actual CORS request.
function makeCorsRequest() {
   
   // All HTML5 Rocks properties support CORS.
   var url = 'http://www.tutorialspoint.com';
   
   var xhr = createCORSRequest('GET', url);
   
   if (!xhr) {
      alert('CORS not supported');
      return;
   }
   
   // Response handlers.
   xhr.onload = function() {
      var text = xhr.responseText;
      var title = getTitle(text);
      alert('Response from CORS request to ' + url + ': ' + title);
   };
   
   xhr.onerror = function() {
      alert('Woops, there was an error making the request.');
   };
   xhr.send();
}

HTML5 - Web RTC

Web RTC introduced by World Wide Web Consortium (W3C). That supports browser-tobrowser applications for voice calling, video chat, and P2P file sharing.

If you want to try out? web RTC available for Chrome, Opera, and Firefox. A good place to start is the simple video chat application at here. Web RTC implements three API's as shown below −

  • MediaStream − get access to the user's camera and microphone.

  • RTCPeerConnection − get access to audio or video calling facility.

  • RTCDataChannel − get access to peer-to-peer communication.

MediaStream

The MediaStream represents synchronized streams of media, For an example, Click on HTML5 Video player in HTML5 demo section or else click here.

The above example contains stream.getAudioTracks() and stream.VideoTracks(). If there is no audio tracks, it returns an empty array and it will check video stream,if webcam connected, stream.getVideoTracks() returns an array of one MediaStreamTrack representing the stream from the webcam. A simple example is chat applications, a chat application gets stream from web camera, rear camera, microphone.

Sample code of MediaStream

function gotStream(stream) {
   window.AudioContext = window.AudioContext || window.webkitAudioContext;
   var audioContext = new AudioContext();
   
   // Create an AudioNode from the stream
   var mediaStreamSource = audioContext.createMediaStreamSource(stream);
   
   // Connect it to destination to hear yourself
   // or any other node for processing!
   mediaStreamSource.connect(audioContext.destination);
}
navigator.getUserMedia({audio:true}, gotStream);

Screen capture

It's also possible in Chrome browser with mediaStreamSource and it requires HTTPS. This feature is not yet available in opera. Sample demo is available at here

Session Control, Network & Media Information

Web RTC required peer-to-peer communication between browsers. This mechanism required signaling, network information, session control and media information. Web developers can choose different mechanism to communicate between the browsers such as SIP or XMPP or any two way communications. A sample example of XHR is here.

Sample code of createSignalingChannel()

var signalingChannel = createSignalingChannel();
var pc;
var configuration = ...;

// run start(true) to initiate a call
function start(isCaller) {
   pc = new RTCPeerConnection(configuration);
   
   // send any ice candidates to the other peer
   pc.onicecandidate = function (evt) {
      signalingChannel.send(JSON.stringify({ "candidate": evt.candidate }));
   };
   
   // once remote stream arrives, show it in the remote video element
   pc.onaddstream = function (evt) {
      remoteView.src = URL.createObjectURL(evt.stream);
   };
   
   // get the local stream, show it in the local video element and send it
   navigator.getUserMedia({ "audio": true, "video": true }, function (stream) {
      selfView.src = URL.createObjectURL(stream);
      pc.addStream(stream);
      
      if (isCaller)
         pc.createOffer(gotDescription);
      
      else
         pc.createAnswer(pc.remoteDescription, gotDescription);
         
         function gotDescription(desc) {
            pc.setLocalDescription(desc);
            signalingChannel.send(JSON.stringify({ "sdp": desc }));
         }
      });
   }
   
   signalingChannel.onmessage = function (evt) {
      if (!pc)
         start(false);
         var signal = JSON.parse(evt.data);
      
      if (signal.sdp)
         pc.setRemoteDescription(new RTCSessionDescription(signal.sdp));
      
      else
         pc.addIceCandidate(new RTCIceCandidate(signal.candidate));
};

Why do front-end developers make significantly less than back-end software engineers?

posted on May 28, 2021

tags:

I have worked in the software industry for many years. I have three children in the industry, one is a graphic designer who also does front end development, one does security and the third is a ‘full stack’ developer. All hold Honours degrees. Their ages are up to 10 years apart, in the order given, so direct comparisons are difficult. I do not have any idea of their actual incomes.

The designer, I believe, is the least highly paid. The other two are exceptionally well paid. I can gauge from their lifestyles that there is a difference.

Some factors, I believe include

  • Risk to the company if the job is not absolutely correct
  • Risk to the company from external threat
  • Perceived and actual complexity
  • Perceived value added
  • Level of training and ONGOING training
  • Risk to the worker of technology migration making their skills obsolete
  • Complexity of the day to day job
  • Required in depth knowledge of the business and business processes to effectively do the job
  • Supply and demand within the skills pool
  • Hard skill vs soft skill. Hard skills can be quantitatively measured, soft skills are more difficult. It is easier to sell a $1M bulldozer than a $1M app or $1M web page design. Yet a web app I know of made $100K for a client in the first day! It continues to do so. The bulldozer is unlikely to ever succeed at this level.
  • Personality - some are focused on the money, others are more driven by other factors. This motivated their choice of career and job selection.
  • Job Market - The job market changed as each of them entered and moved in it. “Full Stack Developer” was not an option when my first child entered the market. Front end and back end were not even concepts when I entered the field.
  • Technology shifts - as per Job market
  • Bleeding edge vs established technology vs obsolete . e.g.
    • COBOL programmers were first poorly paid in the 1950s and early 60s as there was not yet a demand for programming skills.
    • Then better paid in the 70s and 80s as more mainframe computers were introduced. The skills pool was still developing as training had not kept up with demand.
    • By the mid 1990s COBOL became poorly paid in comparison to other newer languages. There was an oversupply as companies and new development shifted to microprocessors and the Internet and COBOL lost favour. The requirement to maintain legacy systems kept the COBOL market buoyant.
    • In the late 1990s there was a spike in demand and pay when companies addressed unexpected Y2K related risk in what were, by now, largely legacy systems.
    • In the 2010s, COBOL once again became exceptionally well paid as the skills pool diminished with many of the remaining programmers retiring or taking on other jobs. Legacy systems still needed maintenance due to changing business requirements.
    • Phasing out some of these vital but legacy systems will prevent problems for their owners in the future if they are unable to migrate away from them. The remaining COBOL systems are large, complex and embed a huge amount of business knowledge, little of which can be recovered from the code or business users. This is largely responsible for the systems not having been replaced and retired. The quality of programmer required to make the necessary changes would, in general, be trained in and know other languages that offer a better career path at this time.

A prof of Psychiatry who had a special interest in HR once told me “Software development is the single most difficult job there is. PERIOD.”

Very few are able to produce good quality code due to the intellectual challenges it presents. Even fewer stick to programming and keep updated as the market shifts.

What’s the future of Java?

posted on May 21, 2021

tags:

Java will almost certainly still be around. Languages don’t die. Some decline in popularity a little, some decline in popularity a lot, and a few stay very popular for a long, long time.

C, for example, is currently the most popular programming language (per the TIOBE Index[1], as of this writing in July 2020) and it’s running neck-in-neck against Java for top spot. All the other competitors are well behind these two front-runners.

C has been around since the early 1970’s. Will Java last as long and be as popular?

There’s a good chance it will.

But a framework like Spring, probably not. Frameworks are ephemeral and constantly changing. Likely as not, something will come along to replace Spring, and whilst Spring will continue to be used, it will decline in popularity until almost no one chooses it any more.

Instead, everyone will want to use the cool new hotness, whatever it is.

But that doesn’t matter. In a long career, you’ll change frameworks and platforms and tools and languages many, many times. It’s how the industry works, and everyone gets used to it.

By the way, GPT-3 is a text-generation toy. It has nothing to do with computer languages, other than being written using one, and being able to create useless code-like pseudo-programs. It certainly won’t replace them.

PHP 101 Basics

posted on May 15, 2021

tags:

PHP is acronym of Hypertext Preprocessor (PHP) is a programming language that allows web developers to create dynamic content that interacts with databases.PHP is basically used for developing web based software applications. One of the most common web hosting services are mainly for PHP.

PHP started out as a small open source project that evolved as more and more people found out how useful it was. Rasmus Lerdorf unleashed the first version of PHP way back in 1994.

Key Points

  • PHP is a recursive acronym for "PHP: Hypertext Preprocessor".

  • PHP is a server side scripting language that is embedded in HTML. It is used to manage dynamic content, databases, session tracking, even build entire e-commerce sites.

  • It is integrated with a number of popular databases, including MySQL, PostgreSQL, Oracle, Sybase, Informix, and Microsoft SQL Server.

  • PHP is pleasingly zippy in its execution, especially when compiled as an Apache module on the Unix side. The MySQL server, once started, executes even very complex queries with huge result sets in record-setting time.

  • PHP supports a large number of major protocols such as POP3, IMAP, and LDAP. PHP4 added support for Java and distributed object architectures (COM and CORBA), making n-tier development a possibility for the first time.

Uses of PHP

PHP has now become a popular scripting language among web developer due to the following reasons −

  • PHP performs system functions, i.e. from files on a system it can create, open, read, write, and close them.

  • PHP can handle forms, i.e. gather data from files, save data to a file, through email you can send data, return data to the user.

  • You add, delete, modify elements within your database through PHP.

  • Access cookies variables and set cookies.

  • Using PHP, you can restrict users to access some pages of your website.

  • It can encrypt data.

Characteristics

Five important characteristics make PHP's practical nature possible −

  • Simplicity

  • Efficiency

  • Security

  • Flexibility

  • Familiarity

"Hello World" Script in PHP

To get a feel for PHP, first start with simple PHP scripts. Since "Hello, World!" is an essential example, first we will create a friendly little "Hello, World!" script.

As mentioned earlier, PHP is embedded in HTML. That means that in amongst your normal HTML (or XHTML if you're cutting-edge) you'll have PHP statements like this −

<html>

   <head>
      <title>Hello World</title>
   </head>
      
   <body>
      <?php echo "Hello, World!";?>
   </body>
      
</html>

It will produce following result −

Hello, World!

If you examine the HTML output of the above example, you'll notice that the PHP code is not present in the file sent from the server to your Web browser. All of the PHP present in the Web page is processed and stripped from the page; the only thing returned to the client from the Web server is pure HTML output.

All PHP code must be included inside one of the three special markup tags ate are recognised by the PHP Parser.

<?php PHP code goes here ?>
<?    PHP code goes here ?>
<script language="php"> PHP code goes here </script>

JavaScript 101 Basics

posted on May 15, 2021

tags:

JavaScript is a lightweight, interpreted programming language with object-oriented capabilities that allows you to build interactivity into otherwise static HTML pages. It is highly used in web hosting as well.

JavaScript code is not compiled but translated by the translator. This translator is embedded into the browser and is responsible for translating javascript code.

Key Points

  • It is Lightweight, interpreted programming language.

  • It is designed for creating network-centric applications.

  • It is complementary to and integrated with Java.

  • It is complementary to and integrated with HTML

  • It is an open and cross-platform

JavaScript Statements

JavaScript statements are the commands to tell the browser to what action to perform. Statements are separated by semicolon (;).

JavaScript statement constitutes the JavaScript code which is translated by the browser line by line.

Example of JavaScript statement:

document.getElementById("demo").innerHTML = "Welcome";

Following table shows the various JavaScript Statements −

Sr.No. StatementDescription
1. switch case A block of statements in which execution of code depends upon different cases. The interpreter checks each case against the value of the expression until a match is found. If nothing matches, a default condition will be used.
2. If else The if statement is the fundamental control statement that allows JavaScript to make decisions and execute statements conditionally.
3. While The purpose of a while loop is to execute a statement or code block repeatedly as long as expression is true. Once expression becomes false, the loop will be exited.
4. do while Block of statements that are executed at least once and continues to be executed while condition is true.
5. for Same as while but initialization, condition and increment/decrement is done in the same line.
6. for in This loop is used to loop through an object's properties.
7. continue The continue statement tells the interpreter to immediately start the next iteration of the loop and skip remaining code block.
8. break The break statement is used to exit a loop early, breaking out of the enclosing curly braces.
9. function A function is a group of reusable code which can be called anywhere in your programme. The keyword function is used to declare a function.
10. return Return statement is used to return a value from a function.
11. var Used to declare a variable.
12. try A block of statements on which error handling is implemented.
13. catch A block of statements that are executed when an error occur.
14. throw Used to throw an error.

JavaScript Comments

JavaScript supports both C-style and C++-style comments, thus:

  • Any text between a // and the end of a line is treated as a comment and is ignored by JavaScript.

  • Any text between the characters /* and */ is treated as a comment. This may span multiple lines.

  • JavaScript also recognizes the HTML comment opening sequence <!--. JavaScript treats this as a single-line comment, just as it does the // comment.-->

  • The HTML comment closing sequence --> is not recognized by JavaScript so it should be written as //-->.

Example

<script language="javascript" type="text/javascript">
   <!--

      // this is a comment. It is similar to comments in C++

      /*
         * This is a multiline comment in JavaScript
         * It is very similar to comments in C Programming
      */
   //-->
<script>

JavaScript variable

Variables are referred as named containers for storing information. We can place data into these containers and then refer to the data simply by naming the container.

Rules to declare variable in JavaScript

Here are the important rules that must be followed while declaring a variable in JavaScript.

  • In JavaScript variable names are case sensitive i.e. a is different from A.

  • Variable name can only be started with a underscore ( _ ) or a letter (from a to z or A to Z), or dollar ( $ ) sign.

  • Numbers (0 to 9) can only be used after a letter.

  • No other special character is allowed in variable name.

Before you use a variable in a JavaScript program, you must declare it. Variables are declared with the var keyword as follows −

<script type="text/javascript">
   <!--
      var money;
      var name, age;
   //-->
</script>

Variables can be initialized at time of declaration or after declaration as follows −

<script type="text/javascript">
   <!--
      var name = "Ali";
      var money;
      money = 2000.50;
   //-->
</script>

Javascript Data Type

There are two kinds of data types as mentioned below −

  • Primitive Data Type

  • Non Primitive Data Type

The following table describes Primitive Data Types available in javaScript

Sr.No.Datatype Description
1. String

Can contain groups of character as single value. It is represented in double quotes.E.g. var x= “tutorial”.

2. Numbers

Contains the numbers with or without decimal. E.g. var x=44, y=44.56;

3. Booleans

Contain only two values either true or false. E.g. var x=true, y= false.

4. Undefined

Variable with no value is called Undefined. E.g. var x;

5. Null

If we assign null to a variable, it becomes empty. E.g. var x=null;

The following table describes Non-Primitive Data Types in javaScript

Sr.No.Datatype Description
1. Array
Can contain groups of values of same type. E.g. var x={1,2,3,55};
2. Objects
Objects are stored in property and value pair. E.g. var rectangle = { length: 5, breadth: 3};

JavaScript Functions

Function is a group of reusable statements (Code) that can be called any where in a program. In javascript function keyword is used to declare or define a function.

Key Points

  • To define a function use function keyword followed by functionname, followed by parentheses ().

  • In parenthesis, we define parameters or attributes.

  • The group of reusabe statements (code) is enclosed in curly braces {}. This code is executed whenever function is called.

Syntax

function functionname (p1, p2) {
   function coding
}

JavaScript Operators

Operators are used to perform operation on one, two or more operands. Operator is represented by a symbol such as +, =, *, % etc. Following are the operators supported by javascript −

  • Arithmetic Operators

  • Comparison Operators

  • Logical (or Relational) Operators

  • Assignment Operators

  • Conditional (or ternary) Operators

  • Arithmetic Operators

Arithmatic Operators

Following table shows all the arithmetic operators supported by javascript −

OperatorDescriptionExample
+ Add two operands. 10 + 10 will give 20
- Subtract second operand from the first. 10 – 10 will give 0
* Multiply two operands. 10 * 30 will give 300
/ Divide numerator by denominator 10/10 will give 1
% It is called modulus operator and gives remainder of the division. 10 % 10 will give 0
++ Increment operator, increases integer value by one 10 ++ will give 11
-- Decrement operator, decreases integer value by one 10 – will give 9

Comparison Operators

Following table shows all the comparison operators supported by javascript −

OperatorDescriptionExample
== Checks if values of two operands are equal or not, If yes then condition becomes true. 10 == 10 will give true
!= Not Equal to operator
Checks if the value of two operands is equal or not, if values are not equal then condition becomes true.
10 !=10 will give false
> Greater Than operator
Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.
20 > 10 will give true
< Less than operator
Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.
10 < 20 will give true
>= Greater than or equal to operator
Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.
10 >=20 will give false
<= Less than or equal to operator
Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.
10 <=20 will give true.

Logical Operators

Following table shows all the logical operators supported by javascript −

OperatorDescriptionExample
&& Logical AND operator returns true if both operands are non zero. 10 && 10 will give true.
|| Logical OR operator returns true If any of the operand is non zero 10 || 0 will give true.
! Logical NOT operator complements the logical state of its operand. ! (10 && 10) will give false.

Assignment Operators

Following table shows all the assignment operators supported by javascript −

OperatorDescriptionExample
= Simple Assignment operator
Assigns values from right side operands to left side operand.
C = A + B will assign value of A + B into C
+= Add AND assignment operator
It adds right operand to the left operand and assign the result to left operand
C += A is equivalent to C = C + A
-= Subtract AND assignment operator
It subtracts right operand from the left operand and assign the result to left operand
C -= A is equivalent to C = C - A
*= Multiply AND assignment operator
It multiplies right operand with the left operand and assign the result to left operand
C *= A is equivalent to C = C * A
/= Divide AND assignment operator
It divides left operand with the right operand and assign the result to left operand
C /= A is equivalent to C = C / A
%= Modulus AND assignment operator
Modulus AND assignment operator, It takes modulus using two operands and assign the result to left operand
C %= A is equivalent to C = C % A

Conditional Operator

It is also called ternary operator, since it has three operands.

OperatorDescriptionExample
?: Conditional Expression If Condition is true? Then value X : Otherwise value Y

Control Structure

Control structure actually controls the flow of execution of a program. Following are the several control structure supported by javascript.

  • if … else

  • switch case

  • do while loop

  • while loop

  • for loop

If … else

The if statement is the fundamental control statement that allows JavaScript to make decisions and execute statements conditionally.

Syntax

if (expression){
   Statement(s) to be executed if expression is true
}

Example

<script type="text/javascript">
   <!--
      var age = 20;
      if( age > 18 ){
         document.write("<b>Qualifies for driving</b>");
      }
   //-->
</script>

Switch case

The basic syntax of the switch statement is to give an expression to evaluate and several different statements to execute based on the value of the expression. The interpreter checks each case against the value of the expression until a match is found. If nothing matches, a default condition will be used.

Syntax

switch (expression) {
   case condition 1: statement(s)
                    break;
   case condition 2: statement(s)
                    break;
   ...
   case condition n: statement(s)
                    break;
   default: statement(s)
}

Example

<script type="text/javascript">
   <!--
      var grade='A';
      document.write("Entering switch block<br/>");
      switch (grade) {
         case 'A': document.write("Good job<br/>");
            break;
         case 'B': document.write("Pretty good<br/>");
            break;
         case 'C': document.write("Passed<br/>");
            break;
         case 'D': document.write("Not so good<br/>");
            break;
         case 'F': document.write("Failed<br/>");
            break;
         default:  document.write("Unknown grade<br/>")
      }
      document.write("Exiting switch block");
   //-->
</script>

Do while Loop

The do...while loop is similar to the while loop except that the condition check happens at the end of the loop. This means that the loop will always be executed at least once, even if the condition is false.

Syntax

do{
   Statement(s) to be executed;
} while (expression);

Example

<script type="text/javascript">
   <!--
      var count = 0;
      document.write("Starting Loop" + "<br/>");
      do{
         document.write("Current Count : " + count + "<br/>");
         count++;
      }while (count < 0);
      document.write("Loop stopped!");
   //-->
</script>

This will produce following result −

Starting Loop
Current Count : 0
Loop stopped! 

While Loop

The purpose of a while loop is to execute a statement or code block repeatedly as long as expression is true. Once expression becomes false, the loop will be exited.

Syntax

while (expression){
   Statement(s) to be executed if expression is true
}

Example

<script type="text/javascript">
   <!--
      var count = 0;
      document.write("Starting Loop" + "<br/>");
      while (count < 10){
         document.write("Current Count : " + count + "<br/>");
         count++;
      }
      document.write("Loop stopped!");
   //-->
</script>

This will produce following result −

Starting Loop
Current Count : 0
Current Count : 1
Current Count : 2
Current Count : 3
Current Count : 4
Current Count : 5
Current Count : 6
Current Count : 7
Current Count : 8
Current Count : 9
Loop stopped! 

For Loop

The for loop is the most compact form of looping and includes the following three important parts −

  • The loop initialization where we initialize our counter to a starting value. The initialization statement is executed before the loop begins.

  • The test statement which will test if the given condition is true or not. If condition is true then code given inside the loop will be executed otherwise loop will come out.

  • The iteration statement where you can increase or decrease your counter.

Syntax

for (initialization; test condition; iteration statement){
   Statement(s) to be executed if test condition is true
}

Example

<script type="text/javascript">
   <!--
      var count;
      document.write("Starting Loop" + "<br/>");
      for(count = 0; count < 10; count++){
         document.write("Current Count : " + count );
         document.write("<br/>");
      }
      document.write("Loop stopped!");
   //-->
</script>

This will produce following result which is similar to while loop −

Starting Loop
Current Count : 0
Current Count : 1
Current Count : 2
Current Count : 3
Current Count : 4
Current Count : 5
Current Count : 6
Current Count : 7
Current Count : 8
Current Count : 9
Loop stopped! 

Creating Sample Program

Following is the sample program that shows time, when we click in button.

<html>
   <body>
      <button onclick="this.innerHTML=Date()">The time is?</button>
      <p>Click to display the date.</p>
      <button onclick="displayDate()">The time is?</button>
      <script>
         function displayDate() {
            document.getElementById("demo").innerHTML = Date();
         }</script>

         <p id="demo"></p>
      </script>
   </body>
</html>

Output

internet_technologies_tutorial

Practice Your HTML, CSS, and JavaScript

posted on May 10, 2021

tags:

There are various ways to practice your HTML, CSS, and JavaScript skills, but before doing anything, it’s important that you ask yourself one simple question that will certainly affect your learning path.

Before learning or practicing any skills, you should ponder on the following questions:

“What is my learning goal?”

“How do I evaluate my current knowledge?”

“How do I learn best? What is my learning style?”

The best way to set up your goals and achieve them is to follow the SMART methodology that stands for Specific, Measurable, Achievable, Relevant, and Time-bound. That will help you determine the direction to move to and will help you choose means to reach your goal in an efficient way.

Gaining insights on where you currently stand will help you realistically look at available options for learning programming languages and understand which option you should go to.

As for the learning style, some of them include (but not limited to) visual, auditory, verbal, mathematical. You might also benefit more from learning alone, or together with someone in a team.

Depending on how you determine your goals and define your learning style, you will have to choose a way to upgrade your skills that suits you best.

Here are some ideas on how to practice HTML, CSS, and JavaScript, based on my 7-year experience as a web app developer.

Take Codeacademy courses “Learn CSS”, “Learn HTML”, “Learn JavaScript”

Codeacademy is one of few platforms where you actually learn by doing. If you get frustrated with reading books and blog posts because you don’t see any results, Codeacademy is your go-to option, as you’ll be constantly creating lines of code and getting instant feedback.

Take personalized interactive courses and solve hands-on challenges with Pluralsight

This is an absolutely groundbreaking platform. With its help, you can measure your skills and identify gaps, apply your HTML, CSS, and JavaScript skills and get guided feedback, take interactive courses, engage in discussions, get useful resources during the course, watch tech conferences and do much more!

Come up with an idea of a website or application

If courses don’t seem to be right up your alley, think of upgrading your skills independently, by creating your own app. I used this method myself and created a weather forecast aggregator back in the day.

Contribute to some open-source project on GitHub

Considering that Github is the biggest development platform, it’s no surprise that you can use it to your advantage when practicing programming language skills. Look for an open-source project and take an active part in development!

Apply for an internship at some software development companies

I know that some junior developers are afraid as hell of applying for internships. The reason behind that is they want to master their skills and only then look for a job. I think this approach is totally wrong because you can already improve and master your skills on real-life projects, with real-life teams and clients if you get to become an intern. There’s nothing to lose.

Learning can be hard and puzzling. I highly recommend you to start actively engaging in projects and creating something of your own. Also, start learning how to deal with web hosting companies.

By the way, as a way of practicing too, I often contribute to writing tech articles

for the company I work for. There are lots of ideas on how to create a specific app, or how to solve tech challenges that might help.

Happy coding!