2. jQuery
• a fast, small, and feature-rich JavaScript library. It
makes things like HTML document traversal and
manipulation, event handling, animation, and
Ajax much simpler with an easy-to-use API that
works across a multitude of browsers. With a
combination of versatility and
extensibility, jQuery has changed the way that
millions of people write JavaScript.
5. jQuery features
• DOM element selections using the multi-browser open
source selector engine Sizzle, a spin-off of the jQuery
project
• DOM traversal and modification (including support for
CSS 1–3)
• DOM manipulation based on CSS selectors that uses
node elements name and node elements attributes (id
and class) as criteria to build selectors
6. • Events
• Effects and animations
• AJAX
• Extensibility through plug-ins
• Utilities - such as user agent information, feature
detection
• Compatibility methods that are natively available in
modern browsers but need fall backs for older ones -
For example the inArray() and each() functions.
• Multi-browser (not to be confused with cross-
browser) support.
7. Including the library
• The jQuery library is a single JavaScript file, containing all of its common
DOM, event, effects, and Ajax functions. It can be included within a web page
by linking to a local copy, or to one of the many copies available from public
servers.
• It is also possible to include jQuery directly from content delivery networks.
<script type= “text/javascript” src= “jquery.js”></script>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js" ></script>
8. Usage styles
• jQuery has two usage styles:
• Via the $ function, which is a factory method for
the jQuery object. These functions, often called
commands, are chainable as they all return
jQuery objects.
• Via $.-prefixed functions. These are utility
functions, which do not act upon the jQuery
object directly.
9. • Typically, access to and manipulation of multiple DOM nodes
begins with the $ function being called with a CSS selector
string, which results in a jQuery object referencing matching
elements in the HTML page. This node set can be manipulated by
calling instance methods on the jQuery object, or on the nodes
themselves. For example:
$("div.test“).add("p.quote").addClass("blue").slideDown("slow");
10. • This line 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
increases their height with an animation. The $ and add functions affect the matched
set, while the addClass and slideDown affect the referenced nodes. Besides accessing
DOM nodes through jQuery object hierarchy, it is also possible to create new DOM
elements if a string passed as the argument to $() looks like HTML. For example, this
line finds an HTML SELECT element with ID="carmakes", and adds an OPTION element
with value "VAG" and text "Volkswagen":
$('select#carmakes').append($('<option />‘).attr({value:"VAG“}).append("Volkswagen"));
11. • The methods prefixed with $. are convenience methods or affect
global properties and behaviour. For example, the following is an
example of the iterating function called each in jQuery
This writes "234" to the document.
$.each([1,2,3], function() {
document.write(this + 1);
});
12. • It is possible to perform browser-independent
Ajax queries using $.ajax and associated methods
to load and manipulate remote data.
This example posts the data name=John and location=Boston to example.php on the server. When this
request finishes successfully, the success function is called to alert the user. If the request fails, it
will alert the user to the failure, the status of the request, and the specific error.
13. jQuery plug-ins
• jQuery's architecture allows developers to create
plug-in code to extend its functionality. Currently
there are thousands of jQuery plug-ins available
on the webthat cover a wide range of
functionality such as Ajax helpers, web
services, datagrids, dynamic lists, XML and XSLT
tools, drag and drop, events, cookie
handling, modal windows, and even a jQuery-
based Commodore 64 emulator.
