Chainability (The Magic of jQuery)

This article is taken from How jQuery Works.

jQuery uses an interesting concept called a "Builder" to make its code short and simple. The Builder pattern is an object-oriented programming design pattern that has been gaining popularity.

In a nutshell: Every method within jQuery returns the query object itself, allowing you to 'chain' upon it, for example:

$("a")
   .filter(".clickme")
     .click(function(){
       alert("You are now leaving the site.");
     })
   .end()
   .filter(".hideme")
     .click(function(){
       $(this).hide();
       return false;
     })
   .end();

Which would work against the following HTML:

<a href="http://google.com/" class="clickme">I give a message when you leave</a>
 <a href="http://yahoo.com/" class="hideme">Click me to hide!</a>
 <a href="http://microsoft.com">I'm a normal link</a>

Methods that modify the jQuery selection and can be undone with end(), are the following:

• add(),
• children(),
• eq(),
• filter(),
• find(),
• gt(),
• lt(),
• next(),
• not(),
• parent(),
• parents() and
• siblings().

Please check the Traversing API documentation for details of these methods.