From Wikipedia, the free encyclopedia

jQuery

Developer(s)	jQuery Team
Stable release	1.4 / 2010-01-14; 3 days ago
Written in	JavaScript
Development status	Active
Type	Web application framework
License	Dual license: GPL and MIT
Website	http://jquery.com/

jQuery is a lightweight cross-browser JavaScript library that emphasizes interaction between JavaScript and HTML. It was released in January 2006 at BarCamp NYC by John Resig. Used at about 20% of the 10,000 biggest websites, jQuery is the most popular JavaScript library in use today.^[1]

jQuery is free, open source software, dual-licensed under the MIT License and the GNU General Public License, Version 2.^[2] jQuery's syntax is designed to make it easier to navigate a document, select DOM elements, create animations, event handling, and Ajax development. jQuery also provides capabilities for developers to create plugins on top of the JavaScript library. Providing this option, developers are able to create abstractions for low-level interaction and animation, advanced effects and high-level, theme-able widgets. This contributes to the creation of powerful and dynamic web pages.

Microsoft and Nokia have announced plans to bundle jQuery on their platforms,^[3] Microsoft adopting it initially within Visual Studio^[4] for use within Microsoft's ASP.NET AJAX framework and ASP.NET MVC Framework whilst Nokia will integrate it into their Web Run-Time platform.

Features

jQuery contains the following features:

• DOM element selections using the cross-browser open source selector engine Sizzle, a spin-off out of the jQuery project^[5]
• DOM traversal and modification (including support for CSS 1-3)
• Events
• CSS manipulation
• Effects and animations
• Ajax
• Extensibility through plugins
• Utilities - such as browser version and the each function.

Use

jQuery usually exists as a single JavaScript file, containing all the common DOM, Event, Effects, and Ajax functions. It can be included within a web page using the following mark-up:

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

jQuery can also be accessed, loaded, and run just as JavaScript has always been^[6]:

jQuery can also be loaded using the Google AJAX Libraries API with the following mark-up^[7]:

<script type="text/javascript" src="http://www.google.com/jsapi"></script>
<script>
google.load("jquery", "1.3.2");
</script>

Microsoft hosted jQuery on its AJAX CDN (Content delivery network) making it easy to add the support for jQuery library. CDN serves JavaScript libraries from one of thousands of geo-located edge-cache servers around the world hosted by Microsoft.

<script src="http://ajax.microsoft.com/ajax/jquery/jquery-1.3.2.min.js" type="text/javascript"></script>

jQuery has two styles of interaction:

• via the $ function, which is a factory method for the jQuery object. These functions, often called commands, are chainable; they each return the jQuery object
• via $.-prefixed functions. These are utility functions which do not work on the jQuery object per se.

A typical workflow for manipulation of multiple DOM nodes begins with the $ function being called with a CSS selector string, which results in the jQuery object referencing zero or more elements in the HTML page. This node set can be manipulated by applying instance methods to the jQuery object, or the nodes themselves can be manipulated. For example:

$("div.test").add("p.quote").addClass("blue").slideDown("slow");

...finds the union of all div tags with class attribute test and all p tags with CSS class attribute quote, adds the class attribute blue to each matched element, and then slides them down with an animation. The $ and add functions affect the matched set, while the addClass and slideDown affect the referenced nodes.

The methods prefixed with $. are convenience methods or affect global properties and behaviour. For example, the following is an example of the map function called each in jQuery:

$.each([1,2,3], function() {
  document.write(this + 1);
});

... writes the numbers 234 to the document.

It is possible to perform browser-independent Ajax queries using $.ajax and associated methods to load and manipulate remote data.

$.ajax({
  type: "POST",
  url: "some.php",
  data: "name=John&location=Boston",
  success: function(msg){
    alert( "Data Saved: " + msg );
  }
});

... will request some.php from the server with parameters name=John and location=Boston and when the request is finished successfully, the success function will be called to alert the user.

Release history

See also

Free software portal

• Comparison of JavaScript frameworks

Notes

References

Bibliography

External links

• Official website
• jQuery Plugin Development A set of articles that explain building custom jQuery plugins.
• Quick Reference Api
• Simplify Ajax development with jQuery
• Dmitri Gaskin (speaker). (2008-04-03) (YouTube). jQuery. Google Tech Talks. http://www.youtube.com/watch?v=8mwKq7_JlS8. Retrieved 2009-05-04.  
• OOP in jQuery: a small article outlining problems using OOP with jQuery, with several workarounds.
• JQuery intro for a C# developer: blog spot that explains jquery using analogy to LINQ.