I would rank the languages in this order:
1) JavaScript
2) Python
3) Ruby
Here's why...
You could just do Python, but if you have the energy and time, solid knowledge of JavaScript can only help you. It's everywhere and not going away.
As for Ruby, my impression of Ruby developers is that they're generally very smart, careful programmers.
You could say this is silly, but if you step back, you do see a general style that goes with a specific language.
That said, the choice of languages and frameworks when Ruby and ROR came to the party are very different than they are now.
ROR offered a rapid application development (RAD) platform that appealed to developers who had to get things done fast, but also appreciated elegant code.
Ruby experts are doing very well (pay rate and availability of jobs), but if you're just getting started, I wouldn't start with Ruby.
I think JavaScript/Python are a better pair considering the current (and what I imagine to be future) market.
As for choosing a language by hourly rate, be careful there.
I was one of the highest-paid Macintosh C programmers I knew (in about 1994) until the work completely disappeared.
There's a time when companies still have ongoing projects in a language/framework and need resources. When new people aren't learning the language and old people are leaving, supply and demand causes rates to rise. Then the whole market disappears.
Choosing between MySQL vs PostgreSQL vs SQL Server
The choice between SQL and non-SQL databases usually boils down to differences in the structure. However, when we are looking into several SQL solutions, the criteria are a lot more distorted. Now will consider the aspects more precisely and analyze the underlying functionality. We’ll be taking a look at the three most popular relational databases: MySQL vs Postgresql vs SQL server.
To help you, we have collected advice from our database developers, re-went through manuals, and even looked up official in-depth guides. We do tend to have our personal preferences, but in this guide, we will put them aside in favor of objective comparison.
MySQL
MySQL happens to be one of the most popular databases, according to DB Engines Ranking. It’s a definite leader among SQL solutions, used by Google, LinkedIn, Amazon, Netflix, Twitter, and others. MySQL popularity has been growing a lot because teams increasingly prefer open-source solutions instead of commercial ones.
Price: the database solution is developed by Oracle and has additional paid tools; the core functionality can be accessed for free.
Language: MySQL is written in C++; database management is done with Structured Query Language.
Read our comparison of MongoDB vs MySQL to make the right choice of a database solution.
PostgreSQL
A tried-and-proven relational database that is known for supporting a lot of data types, intuitive storage of schemaless data, and rich functionality. Some developers go even as far as to claim that it’s the most advanced open-source database on the market. We wouldn’t go that far, but it’s definitely a highly universal solution.
Price: open-source
Language: C
SQL Server
Unlike Postgresql vs MySQL, SQL Server is a commercial solution. It’s preferred by companies who are dealing with large traffic workloads on a regular basis. It’s also considered to be one of the most compatible systems with Windows services.
The SQL Server infrastructure includes a lot of additional tools, like reporting services, integration systems, and analytics. For companies that manage multiple teams, these tools make a big difference in day-to-day work.
Price: the database has a free edition for developers and small businesses but only supports 1 processor, 1GB of maximum memory used by the database engine and 10GB maximum database size.
. For a server, users need to pay $931.
Side-by-side Comparison of SQL Tools
In this comparison, we’ll take a look at the functionality of the three most popular SQL databases, examine their use cases, respective advantages, and disadvantages. Firstly, we’ll start by exploring the in-depth functionality.
Data Changes
Here we evaluate the ease that the data can be modified with and the database defragmented. The key priority is the systems’ flexibility, security, and usability.
Row updates
This criterion refers to the algorithms that a database uses to update its contents, speed, and efficiency.
In the MySQL case, a solution updates data automatically to the rollback storage. If something goes wrong, developers can always go back to the previous version.
PostgreSQL: developers insert a new column and row in order to update the database. All updated rows have unique IDs. This multiplies the number of columns and rows and increases the size of the database, but in turn, developers benefit from higher readability.
SQL Server: the database has three engines that are responsible for row updates. The ROW Store handles the information on all previous row updates, IDs, and modified content. The in-memory engine allows analyzing the quality of an updated database with a garbage collector. The column-store database lets store updates in columns, like in column-driven databases.
Among these three, SQL Server offers perhaps the most flexibility and efficiency, because it allows monitoring updated rows and columns, collecting errors, and automating the process. The difference between SQL Server and MySQL and Postgresql lies mainly in customizing the positions – SQL Server offers a lot more than others.
Defragmentation
When developers update different parts of an SQL database, the changes occur at different points of the systems and can be hard to read, track, and manage. Therefore, maintenance should include defragmentation – the process of unifying the updated database by assigning indexes, revisiting the structure, and creating new pages. The database frees up the disk space that is not used properly so that a database can run faster.
MySQL offers several approaches to defragmentation – during backup, index creation, and with an OPTIMIZE Table command. Without going into much detail, we’ll just say that having that many options for table maintenance is convenient for developers, and it surely saves a lot of time.
PostgreSQL allows scanning the entire tables of a data layer to find empty rows and delete the unnecessary elements. By doing so, the system frees up the disk space. However, the method requires a lot of CPU and can affect the application’s performance.
SQL Server offers an efficient garbage collector that doesn’t create more than 15-20% of overhead. Technically, developers can even run garbage collector on a continuous basis, because it’s that efficient.
Overall, MySQL and SQL Server offer more of defragmentation methods that Postgresql does. They consume less CPU and provide more flexible settings.
Data Queries
Here, we take a look at how the systems cache and process user requests, what approaches they take in storing data, and how developers can manage it.
Buffer Pool
Some systems call a buffer to pull cache, but regardless of terminology, our goal is to summarize the algorithms that systems use to process user queries and maintain connections.
MySQL offers a scalable buffer pool – developers can set up the size of the cache according to the workload. If the goal is to save CPU and storage space, developers can put strict benchmarks on their buffer pool. Moreover, MySQL allows dividing cache by segments to store different data types and maximize isolation.
PostgreSQL isolates processes even further than MySQL by treating them as a separate OS process. Each database has a separate memory and runs its own process. On the one hand, management and monitoring become a lot easier, but on the other, scaling multiple databases takes a lot of time and computing resources.
SQL Server also uses a buffer pool, and just like in MySQL, it can be limited or increased according to processing needs. All the work is done in a single pool, with no multiple pages, like in Postgresql.
If your priority is to save computing resources and storage, choose flexible solutions: the choice will be between MySQL vs SQL Server. However, if you prefer clear organization and long-term order, Postgre, with its isolated approach, might be a better fit.
Temporary Tables
Temporary tables allow storing intermediate results from complex procedures and branched business logic. If you need some information only to power the next process, it doesn’t make sense to store it in a regular table. Temporary tables improve database performance and organization by separating intermediary data from the essential information.
MySQL offers limited functionality for temporary tables. Developers cannot set variables or create global templates. The software even limits the number of times that a temporary table can be referred to – not more than once.
Postgresql offers a lot more functionality when it comes to temporary content. You divide temporary tables into local and global and configure them with flexible variables.
SQL Server also offers rich functionality for temporary table management. You can create local and global temporary tables, as well as oversee and create variables.
Temporary tables are essential for applications with complicated business logic. If your software runs a lot of complex processes, you will need to store multiple intermediary results. Having rich customization functionality will often be necessary throughout the development process.
Indexes
The way a database handles indexes is essential because they are used to locate data without searching for a particular row. Indexes can refer to multiple rows and columns. You can assign the same index to files, located in the different places in the database, and collect all these pieces with a single search.
In this comparison, we evaluated the way indexes are created in every solution, the support of multiple-index searches, and multi-column indexes, as well as partial ones.
MySQL organized indexes in tables and clusters. Developers can automatically locate and update indexes in their databases. The search isn’t highly flexible – you can’t search for multiple indexes in a single query. MySQL supports multi-column indexes, allowing adding up to 16 columns.
Postgresql also supports index-based table organization, but the early versions don’t include automated index updates (which appear only after the 11th edition release). The solution also allows looking up many indexes in a single search, which means that you can find a lot of information. The multi-column settings are also more flexible than in MySQL – developers can include up to 32 columns.
SQL Server offers rich automated functionality for index management. They can organize in clusters and maintain the correct row order without manual involvement. The solution also supports multiple-index searches and partial indexes.
Having flexible index settings allows looking up information faster and organizing multiple data simultaneously.
Memory-Optimized Tables
Memory-optimized tables are mainly known as a SQL Server concept, but they also exist in other database management solutions. Such a table is stored in active memory and on the disk space in a simplified way. To increase the transaction speed, the application can simply access data directly on the disk, without blocking concurrent transactions. For processes that happen on a regular basis and usually require a lot of time, a memory-optimized table can be a solution to improve database performance.
MySQL supports the memory-stored table, but it can’t participate in transactions, and its security is highly vulnerable. Such tables are used only for reading purposes and can simplify exclusively primitive operations. For now, MySQL doesn’t come close to making the most out of memory-optimized tables.
PostgreSQL doesn’t support in-memory database creation.
SQL Server uses an optimistic strategy to handle memory-optimized tables, which means they can participate in transactions along with ordinary tables. Memory-based transactions are faster than regular ones, and this allows a drastic increase in application speed.
As expected, memory-optimized tables are best set up in MySQL – it’s basically their native approach. It’s not an essential database feature, but still, a good way to improve performance.
JSON Support
The use of JSON files allows developers to store non-numeric data and achieve faster performance. JSON documents don’t have to be parsed, which contributes to much higher processing speed. They are easily readable and accessible, which is why JSON support simplifies maintenance. JSON files are mostly used in non-relational databases, but lately, SQL solutions have supported this format as well.
MySQL supports JSON files but doesn’t allow indexing them. Overall, the functionality for JSON files in MySQL is very limited, and developers mostly prefer using classical strings. Similarly to non-relational databases, MySQL also allows working with geospatial data, although handling it isn’t quite as intuitive.
Postgresql supports JSON files, as well as their indexing and partial updates. The database supports even more additional data than MySQL. Users can upload user-defined types, geospatial data, create multi-dimensional arrays, and a lot more.
SQL Server also provides full support of JSON documents, their updates, functionality, and maintenance. It has a lot of additional features for GPS data, user-defined types, hierarchical information, etc.
Overall, all three solutions are pretty universal and offer a lot of functionality for non-standard data types. MySQL, however, puts multiple limitations for JSON files, but other than that, it’s highly compatible with advanced data.
Replication and Sharding
When the application grows, a single server can no longer accommodate all the workload. Navigating single storage becomes complicated, and developers prefer to migrate to different ones or, at least, create partitions. The process of partitioning is the creation of many compartments for data in the single process.
Partitioning
Replacing is easier in NoSQL databases because they support horizontal scaling rather than vertical – increasing the number of locations rather than the size of a single one. Still, it’s possible to distribute data among different compartments even in SQL solutions, even if it’s slightly less efficient.
MySQL allows partitioning databases with hashing functions in order to distribute data among several nodes. Developers can generate a specific partition key that will define the data location. Hashing permits avoiding bottlenecks and simplifying maintenance.
Postgresql allows making LIST and RANGE partitions where the index of a partition is created manually. Developers need to identify children and parent column before assigning a partition for them.
SQL Server also provides access to RANGE partitioning, where the partition is assigned to all values that fall into a particular range. If the data lies within the threshold, it will be moved to the partition.
Ecosystem
The database ecosystem is important because it defines the frequency of updates, the availability of learning resources, the demand on the market, and the tool’s long-term legacy.
MySQL Ecosystem
MySQL is a part of the Oracle ecosystem. It’s the biggest SQL database on the market with a large open-source community. Developers can either purchase commercial add-ons, developed by the Oracle team or use freeware installations. You will easily find tools for database management, monitoring, optimization, and learning. The database itself is easy to install – all you have to do is pretty much download the installer.
MySQL has been a reliable database solution for 25 years, and statistics don’t pinpoint at any sights of its decline. It looks like MySQL will keep holding a leading position not only among SQL tools but also among all the databases in general.
Postgresql Ecosystem
The Postgresql community offers a lot of tools for software scaling and optimization. You can find add-ons by your industry – take a look at the full list on the official page. The integrations allow developers to perform clustering, integrating AI, collaborating, tracking issues, improving object mapping, and cover many other essential features.
Some developers point out that Postgresql’s installation process is slightly complicated – you can take a look at its official tutorial. Unlike MySQL, which can run right away, Postgresql requires additional installations.
SQL Server Ecosystem
SQL Server is highly compatible with Windows and all Microsoft OS and tools. If you are working with Windows, SQL server is definitely the best option on the market. Users of the database receive access to many additional instruments that cover server monitoring (Navicat Monitor), data analysis, parsing (SQL Parser), and safety management software (DBHawk).
SQL Server ecosystem is oriented towards large infrastructures. It’s more expensive than open-source competitors, but at the end of the day, users get access to frequently updated official ecosystem and active customer support.
What is the difference between SQL and MySQL? MySQL is an open-source database, whereas SQL Server is a commercial one. MySQL is more popular, but SQL Server comes close.
Popularity
For a start, we analyzed the DB Engines ratings of every compared engine. The leader is MySQL, with second place as the most popular database and second most popular relational solution. SQL Server takes third place, while PostgreSQL is ranked fourth.
The statistics by Statista shows the same tendency. MySQL is ranked second, leaving the leading position to Oracle, the most popular DBMS today. SQL Server follows with a slim difference, whereas Postgresql, which comes right after, is a lot less recognized.
MySQL, therefore, is the most demanded database on the market, which means finding competent teams, learning resources, reusable libraries, and ready add-ons will be easy. So, if you are choosing between SQL Server vs MySQL in terms of market trends, the latter is a better choice.
Companies using MySQL
- Udemy
- Netflix
- Airbnb
- Amazon
MySQL is used widely by big corporations and governmental organizations. Over the last 25 years, the solution has built a reputation of a reliable database management solution, and as time shows, it’s indeed capable of supporting long-running projects.
Companies that use PostgreSQL
- Apple
- Skype
- Cisco
- Etsy
Postgre is known for its intuitive functionality and versatile security settings. This is why its main use cases are governmental platforms, messenger applications, video chats, and e-commerce platforms.
Companies using SQL Server
- JPMorganChase
- Bank of America
- UPS
- Houston Methodist
SQL Server is a go-to choice for large enterprises that have vast business logic and handle multiple applications simultaneously. Teams that prioritize efficiency and reliability over scalability and costs typically choose this database. It’s a common option for “traditional” industries – finances, security, manufacturing, and others.
Conclusion
The choice between the three most popular databases ultimately boils down to the comparison of the functionality, use cases, and ecosystems. Companies that prioritize flexibility, cost-efficiency, and innovation usually choose open-source solutions. They can be integrated with multiple free add-ons, have active user communities, and are continuously updated.
For corporations that prefer traditional commercial solutions, software like SQL Server backed up by a big corporation and compatible with an extensive infrastructure, is a better bet. They have access to constant technical support, personalized assistance, and professional management tools.
If you are considering a database for your project, getting a team of experts who will help you define the criteria and narrow down the options is probably the best idea. You can always get in touch with our database developers – we will create a tech stack for your product and share our development experience.
What is the easiest JavaScript framework to learn?
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?
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.
Moving to PHP 7.4 and Discontinuing Some Old Versions
Moving to PHP 7.4 as the server default
As of June 2021, we will be switching the default version on our servers to PHP 7.4. This means that all new sites will be using 7.4, unless manually switched to a different one. PHP 7.4 has been around for more than 2 years now and has already become widely compatible with different CMS’s, themes and plugins, where PHP 7.3 (our current default) is already out of active support and will get out of security support too by the end of this year. Keeping your PHP version up to date has undeniable performance and security advantages and that is why we are now helping you switch to PHP 7.4.
All websites using our Managed PHP service will also be upgraded to 7.4 in the period June 10-21, 2021. PHP 7.3 will still be available on our servers and can be set up manually for any site by our clients from Site Tools > Dev > PHP Manager.
Discontinuing support for 7.2, 7.1, 7.0, 5.6 and lower at the end of the year
At the same time, the security support for all PHP versions below 7.3 has been officially over for quite some time, and given the exploits that leak out once in a while, we believe the risk of using them is growing higher. Additionally, the performance of websites using old PHP versions is considerably lower compared to sites using newer versions. That is why we are starting a process of discontinuation of PHP 7.2, 7.1, 7.0, 5.6 and lower on our servers. After June 21, 2021 we will be gradually updating the sites using old PHP versions to PHP 7.4. PHP versions below 7.3 will no longer be supported on our servers after December 31, 2021.
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What to do if you are using an old PHP version?
This PHP update will affect many websites on our platform. That is why we have started communicating the update one month ago and we strongly encourage you to evaluate the impact of upgrading to 7.4 on your site as soon as possible by using this tool:
your-domain.com/.well-known/sg-php-try-v74
To see if a site will work properly after the upgrade, please type the above URL using your own site domain in the browser and browse through the site, its subdomains (if any) and its admin area. If anything does not look or behave as expected, we highly recommend that you further investigate your site compatibility with PHP 7.4 and fix any issues before the update. If you have broken plugins or a theme, consider updating or replacing them. If that’s too hard, or the problem is elsewhere, contact your developers for assistance.
Note: By opening your website through the link above you will browse it using PHP 7.4. This change affects ONLY your current browser session. All other visitors will continue to access your site with its current PHP version. To stop the compatibility check browsing mode in your own browser, please close the browser and access your site again via its standard URL.
Magento special case: Sites using Magento 2.3.6 or lower are not compatible with PHP 7.4 That is why, if you have such a website, we strongly recommend you update it to 2.3.7 as soon as possible, so that it is compatible with PHP 7.4 and ready for the PHP upgrade.
We are aware that sites currently using PHP version 7.2 or lower may need longer time to fix possible incompatibilities with PHP 7.4. That is why, the owners of such sites were provided with a link for possible opt-out in the email about the update, sent over the past few days. By opting out through this link, clients confirm that they do not want us to update their site PHP version for them, but are aware that this version will nonetheless stop functioning after December 31, 2021.
For clients using PHP 7.3, we strongly recommend that they do not postpone their PHP update, but in case this is really needed they may simply switch to manual PHP version management, until their site is ready for PHP 7.4.
Looking forward to seeing more secure and much faster sites after the update!
JavaScript Tutorial
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 −
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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.
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Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something.
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Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.
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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 −
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Client-side JavaScript does not allow the reading or writing of files. This has been kept for security reason.
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JavaScript cannot be used for networking applications because there is no such support available.
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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 −
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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.
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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.
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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 −
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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.
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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.
<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 −
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Any text between a // and the end of a line is treated as a comment and is ignored by JavaScript.
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Any text between the characters /* and */ is treated as a comment. This may span multiple lines.
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JavaScript also recognizes the HTML comment opening sequence <!--. JavaScript treats this as a single-line comment, just as it does the // comment.
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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 −
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Follow Tools → Internet Options from the menu.
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Select Security tab from the dialog box.
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Click the Custom Level button.
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Scroll down till you find Scripting option.
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Select Enable radio button under Active scripting.
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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 −
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Open a new tab → type about: config in the address bar.
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Then you will find the warning dialog. Select I’ll be careful, I promise!
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Then you will find the list of configure options in the browser.
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In the search bar, type javascript.enabled.
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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 −
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Click the Chrome menu at the top right hand corner of your browser.
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Select Settings.
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Click Show advanced settings at the end of the page.
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Under the Privacy section, click the Content settings button.
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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 −
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Follow Tools → Preferences from the menu.
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Select Advanced option from the dialog box.
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Select Content from the listed items.
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Select Enable JavaScript checkbox.
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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 −
<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.
<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 −
<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.
<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.
<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.
<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.
<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.
<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.
<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.
<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.
<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.
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.
<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.
<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.
<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.
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.
<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.
<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 −
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.
<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 −
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.
<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 −
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The loop initialization where we initialize our counter to a starting value. The initialization statement is executed before the loop begins.
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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.
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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 −
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.
<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.
<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 −
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 −
<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 −
<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.
<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
<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.
<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.
<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.
<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.
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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.
<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.
<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.
<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.
<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.
<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.
<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.
<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.
<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
<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
<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 −
<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 −
<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.
<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.
<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.
<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 −
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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.
<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.
<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.
<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.
<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 −
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JavaScript Number Object
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JavaScript Boolean Object
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JavaScript String Object
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JavaScript Array Object
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JavaScript Date Object
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JavaScript Math Object
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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.
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date − Integer value representing the day of the month.
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hour − Integer value representing the hour of the day (24-hour scale).
-
minute − Integer value representing the minute segment of a time reading.
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second − Integer value representing the second segment of a time reading.
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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
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 ⁢ −
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.
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 −
|
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 ]
|
2 |
dataTransfer.effectAllowed [ = value ]
|
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 −
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?
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 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?
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 & MySQL – Environment Setup Basics
In order to develop and run PHP Web pages, three vital components need to be installed on your computer system.
-
Web Server − PHP works with virtually all Web Server software, including Microsoft's Internet Information Server (IIS) but most often used is Apache Server. Download Apache for free here − https://httpd.apache.org/download.cgi
-
Database − PHP works with virtually all database software, including Oracle and Sybase but most commonly used is MySQL database. Download MySQL for free here − https://www.mysql.com/downloads/
-
PHP Parser − In order to process PHP script instructions, a parser must be installed to generate HTML output that can be sent to the Web Browser. This tutorial will guide you how to install PHP parser on your computer.
PHP Parser Installation
Before you proceed, it is important to make sure that you have proper environment setup on your machine to develop your web programs using PHP. Store the following php file in Apache's htdocs folder.
phpinfo.php
<?php phpinfo(); ?>
Type the following address into your browser's address box.
http://127.0.0.1/phpinfo.php
If this displays a page showing your PHP installation related information, then it means you have PHP and Webserver installed properly. Otherwise, you have to follow the given procedure to install PHP on your computer.
This section will guide you to install and configure PHP over the following four platforms −
Apache Configuration
If you are using Apache as a Web Server, then this section will guide you to edit Apache Configuration Files.
Check here − PHP Configuration in Apache Server
PHP.INI File Configuration
The PHP configuration file, php.ini, is the final and immediate way to affect PHP's functionality.
Check here − PHP.INI File Configuration
Windows IIS Configuration
To configure IIS on your Windows machine, you can refer your IIS Reference Manual shipped along with IIS.
Install MySQL Database
The most important thing you will need, of course is an actual running database with a table that you can query and modify.
-
MySQL DB − MySQL is an open source database. You can download it from MySQL Official Site. We recommend downloading the full Windows installation.
-
In addition, download and install MySQL Administrator as well as MySQL Query Browser. These are GUI based tools that will make your development much easier.
-
Finally, download and unzip MySQL Connector/J (the MySQL JDBC driver) in a convenient directory. For the purpose of this tutorial we will assume that you have installed the driver at C:Program FilesMySQLmysql-connector-java-5.1.8.
-
Accordingly, set CLASSPATH variable to C:Program FilesMySQLmysql-connector-java-5.1.8mysql-connector-java-5.1.8-bin.jar. Your driver version may vary based on your installation.
Set Database Credential
When we install MySQL database, its administrator ID is set to root and it gives provision to set a password of your choice.
Using root ID and password you can either create another user ID and password, or you can use root ID and password for your JDBC application.
There are various database operations like database creation and deletion, which would need administrator ID and password.
For rest of the JDBC tutorial, we would use MySQL Database with guest as ID and guest123 as password.
If you do not have sufficient privilege to create new users, then you can ask your Database Administrator (DBA) to create a user ID and password for you.
Create Database
To create the TUTORIALSPOINT database, use the following steps −
Step 1
Open a Command Prompt and change to the installation directory as follows −
C:> C:>cd Program FilesMySQLin C:Program FilesMySQLin>
Note − The path to mysqld.exe may vary depending on the install location of MySQL on your system. You can also check documentation on how to start and stop your database server.
Step 2
Start the database server by executing the following command, if it is already not running.
C:Program FilesMySQLin>mysqld C:Program FilesMySQLin>
Step 3
Create the TUTORIALSPOINT database by executing the following command −
C:Program FilesMySQLin> mysqladmin create TUTORIALSPOINT -u guest -p Enter password: ******** C:Program FilesMySQLin>
Create Table
To create the Employees table in TUTORIALSPOINT database, use the following steps −
Step 1
Open a Command Prompt and change to the installation directory as follows −
C:> C:>cd Program FilesMySQLin C:Program FilesMySQLin>
Step 2
Login to the database as follows −
C:Program FilesMySQLin>mysql -u guest -p Enter password: ******** mysql>
Step 3
Create the table Employees as follows −
mysql> use TUTORIALSPOINT; mysql> create table Employees -> ( -> id int not null, -> age int not null, -> first varchar (255), -> last varchar (255) -> ); Query OK, 0 rows affected (0.08 sec) mysql>
Create Data Records
Finally you create few records in Employee table as follows −
mysql> INSERT INTO Employees VALUES (100, 18, 'Zara', 'Ali'); Query OK, 1 row affected (0.05 sec) mysql> INSERT INTO Employees VALUES (101, 25, 'Mahnaz', 'Fatma'); Query OK, 1 row affected (0.00 sec) mysql> INSERT INTO Employees VALUES (102, 30, 'Zaid', 'Khan'); Query OK, 1 row affected (0.00 sec) mysql> INSERT INTO Employees VALUES (103, 28, 'Sumit', 'Mittal'); Query OK, 1 row affected (0.00 sec) mysql>
PHP 101 Basics
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>
Which is Better – PHP or Python?
Firstly, define “better”? That’s an incredibly subjective term that depends entirely on what you’re looking for. Do you mean faster? More widely used? Easier? Offers greater employment prospects? Greater availability of frameworks and libraries? I could go on.
PYTHON
What are Python’s strengths?
- Vast array of built-in and 3rd party libraries/modules specifically for web development and server management (server management applies to web development too).
- Those 3rd party libraries are well designed, well maintained, easy to install and powerful.
- Ease of development. If you’ve ever programmed in Python, you know how easy it is.
- Django is very powerful. It helps replace JavaScript and PHP.
- [OPINION] Personally, I hate PHP and JavaScript. They’re frustrating to use and both are vulnerability prone. PHP more because of flaws in the language; JavaScript because of flaws in the weird-as-hell specification that lead to poor interpretations of how the JS engine should be implemented.
- Fully object oriented.
- Great for data manipulation and machine learning (can be important if you’re providing targeted advertising on your platform).
- With the right framework, and modules (included as standard), you can properly and nicely integrate with a database server and auto-generate queries for your site.
- e.g. If user is searching their account for a specific license key, the framework handles that by translating what the user’s doing into an SQL query.
- e.g. #2: If the admin is searching for a customer by email address, the framework will translate that into an SQL query, then translate the results back and display them in CSS-formatted HTML.
What are Python’s weaknesses?
- Slow. Like really slow. Slower than Python fanboys like to admit. As Oluwasegun said, PHP is up to 3x faster (sometimes more, sometimes less, depends).
- When you use it for development, you can’t really think of it like you’re using Python: You’re using a framework (e.g. Django). So learning Python isn’t enough, you have to learn the framework too.
- Python is nowhere near as widely used as PHP, so its employability factor, specifically in regards to web development, is much more limited. I heard a stat that ~80% of all websites use PHP - I can’t verify the stat, but it wouldn’t surprise me.
- This kind of goes hand-in-hand with slowness, but needs to be addressed separately: Resource use. Python hogs resources much more than PHP. You’d think, if it utilized so much of the available resources, that would actually maybe help to speed it up…… No, no it doesn’t.
- [Opinion] The OOP aspect of Python is abysmal. If you’ve ever done any OOP in a language like Java, C#, or C++, you’ll understand why I hate it. Any language that relies on this and super() hasn’t done it right. It makes you code look confusing as hell, obfuscates the whole process and makes the developer prone to errors. It’s just not necessary - the whole aspect of the language feels (as I think I’ve said elsewhere on this site) like it was bolted on, with a hammer, by a blind fish…. as an afterthought. And guess what? It was! Alright it wasn’t bolted on using a hammer, by a fish. But it was an afterthought and wasn’t initially intended to be part of the language (it wasn’t initially included).
It’s a poor and restrictive implementation of OOP. Again, Opinion. Some people like it, but they’re usually the ones that say C and C++ are difficult and confusing.
All in all, that’s not terrible right? Personally I think the biggest issue in the above is ‘market share’ in comparison to PHP, from an employability perspective anyway.
PHP
What are PHP’s strengths?
- Very fast.
- Fully object oriented.
- Used in a vast majority of back-end web-services and ‘behind the scenes’ functionality of websites.
- Integrates nicely with SQL servers and virtually all flavours of them.
- Auto-generates queries to the database (see Python section of example of what this means)
- Wonderfully diverse built-in functionality that is designed for web use.
- Lots of PHP web API’s available that further extend what can be done.
- Lots of these are designed specifically for use with PHP and cannot be used with Python & Django e.g. Many e-Commerce API’s
What are PHP’s weaknesses?
Oh boy. There’s some real humdingers:
- [Opinion] The syntax is friggin awful. Yes, that is an opinion, but it’s a very widely shared opinion. Each and every single PHP programmer that I’ve ever spoken to has held this opinion too. If you’re not already familiar with it, check it out.
- SQL injection attacks. See the link below for a detailed explanation of what it is, why it happens and how to solve it using PHP:
- Prevent SQL injection vulnerabilities in PHP applications and fix them
- Remote Code Execution: A bug in a PHP application may accept user input and evaluate it as PHP code.
- Cross-Site Scripting (XSS [X = Cross]): Stored XSS and Reflected XS
- Authentication Bypass - Technically a developer error, but the language itself makes it really, really easy to make this mistake.
I could go on with more, but here’s a link instead:
https://www.wordfence.com/learn/understanding-php-vulnerabilities/
[Opinion] OOP is just as bad as in Python. Possibly worse due to the syntax. It still uses this (but it’s actually $this)
All in all, those vulnerabilities are pretty darned awful, but they’re mostly due to developer error. Get to know PHP well and research not just ‘How me do a PHP develop’, but “PHP development pitfalls” and “PHP vulnerabilities” then it won’t be such an issue.
All Together Now
So what’s the ultimate conclusion to be drawn here? Well, despite what die Python fans like to say, Python cannot fully replace PHP, due to the presence of common PHP-only API’s, and the industry dominance of PHP.
I know I’ve already gone on for ages, but this is my final point and it’s really important to state: The idea that developers should be picking a “one best language because it’s bestest” is a massive failure of both the modern education system, and junior [young] developers. In order to be truly proficient in any field of development, be web, app or software, you’ll need to know multiple languages. The same holds true to be reliably employable.
So in conclusion it’s not about which is better, it’s about understanding where and when to use them. And, for web development, the BARE MINIMUM you should learn are the following:
- HTML
- CSS
- JavaScript
- PHP
- JSON (replace XML)
- SQL (MySQL, Oracle, MS SQL are the 3 main) - beware of different ‘flavours’
- Python
- Web hosting admin panel
The above are absolutely non-negotiable for a career. Optionally, learn Java too. It’s useful for web apps.
Create a Simple URL Shortener With 10 Lines of PHP
I love to solve problems with tiny, one-off scripts. The fewer lines that I have to write, the better. Recently I had another opportunity to do just that. I needed a way to embed links in PDF documents, the destinations of which I might need to update in the future. Links in PDFs can't be updated without generating and sending the files again, which is time consuming. The links were also long, and it would be difficult to type them manually if the documents are printed.
This problem can be solved nicely with a URL shortener. Such services have been around for a long time, but there are a few problems with them:
You depend on an external service - when it is down, all your links are down. Even worse - if it goes out of business, so do your links.
All clicks are being monitored for unknown purposes.
You usually can't change the destination of a short link.
Some services allow you to choose a custom slug, but all the good ones have already been taken.
The stage is set for writing a quick and dirty PHP script!
The Idea
If we are to create a link shortening service that you are the only user of, we might omit things like user registrations and admin panels. Here are some of the features of our link shortener:
Short links will come in the form http://example.com/l/short-link. Visiting this URL will redirect the browser to the real address.
The entire script will be held in a single php file - index.php, without external dependencies.
There won't be an administration screen for adding or editing links. Everything will be handled by a simple text file that sits on your server and which you can edit easily.
There won't be any automatically assigned ids to links - you will choose the short slug yourself.
These requirements greatly simplify the script that we will be writing. To make things even more straightforward, I decided to store the links in an ini file, because it is very easy to edit by hand, and it has native support in PHP via the parse_ini_file function (this will save us from having to read the contents of the file and parsing it ourselves; and as a bonus this function is very fast).
The INI File
Here is what the ini file looks like:
links.ini
google = https://www.google.com/
fb = https://www.facebook.com/
Short link on the left, long link on the right. It doesn't get any simpler than that!
The Code
The PHP script is equally bare bones:
index.php
$links = parse_ini_file('links.ini');
if(isset($_GET['l']) && array_key_exists($_GET['l'], $links)){
header('Location: ' . $links[$_GET['l']]);
}
else{
header('HTTP/1.0 404 Not Found');
echo 'Unknown link.';
}
The script expects to receive the slug in $_GET['l'] like so: http://example.com/index.php?l=google. This obviously is not very short, but we can make it prettier with an .htaccess file (assuming you are running the Apache webserver).
.htaccess
RewriteEngine On
RewriteCond $1 !^(index.php)
RewriteRule ^(.*)$ index.php?l=$1 [L]
This file should sit in the same folder, next to index.php and links.ini. What it does, is to route every request for a file that is not index.php, to index.php?l=xxx. This prevents infinite loops and also makes links.ini unreachable from a browser.
For the best result, place these three files in a folder with a short name like 'l' in the root of your website, and you will get short links like http://example.com/l/google. (Obviously google.com is a poor choice in this case - the short link is longer than the original!)
We're Done!
If you don't want to keep a separate file with links, you might eliminate it entirely by placing the short links directly in the script as an associative array. Another improvement might be to build a simple administrative interface that changes the contents of the ini file. I am sure that there even more awesome things that you can do with this code. I hope that you find this tiny script useful!