Jquery
jQuery is a lightweight JavaScript library that emphasizes interaction between JavaScript and HTML. It was released in January 2006 at BarCamp NYC by John Resi
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Just as CSS separates “display” characteristics from the HTML structure, jQuery separates the “behavior” characteristics from the HTML structure. For example, instead of directly specifying the on-click event handler in the specification of a button element, a jQuery driven page would first identify the button element, and then modify its on-click event handler. This separation of behavior from structure is also referred to as the principle of Unobtrusive JavaScript.
jQuery contains the following features:
* DOM element selections using the cross-browser open source selector engine Sizzle, a spin-off out of jQuery project
* DOM traversal and modification (including support for CSS 1-3 and basic XPath)
* Events
* CSS manipulation
* Effects and animations
* Ajax
* Extensibility
* Utilities – such as browser version and the each function.
* JavaScript Plugins
jQuery usually exists as a single JavaScript file, containing all the common DOM, Event, Effects, and Ajax functions. It can be included within any web page by using the following mark-up:
<script type=”text/javascript” src=”/path/to/jQuery.js”></script>
To execute a function ‘myfunc’ immediately after the page is loaded (called the ready handler in jQuery lingo):
$(document).ready(function() {
myfunc();
});
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 $ 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 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 234 to the document.
It is possible to perform Ajax routines using the $.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 with parameters name=John and location=Boston and when the request is finished successfully, the response will be alerted.
Here is a simple good JQuery demo for an expanable sidebarmenu, including animation, button event, ….
http://www.vimeo.com/116991/
Tags: $, CSS, javascript, Jquery
