= JavaScript for Trac and plugin development =

JavaScript is used in Trac to add dynamics to web interface elements on the browser side:
 * expanding/folding in TracBrowser
 * providing [TracKeys keyboard shortcuts]
 * ...

{{{
#!comment
list other uses of JS in Trac
}}}

=== jQuery ===

Trac makes heavy use of [http://en.wikipedia.org/wiki/JQuery jQuery] library to ease development. Access to this library contents is usually provided through the main function named $. $ as a name used for brevity and clarity. Unfortunately, other libraries may use it too and this may cause conflicts. $ in fact is just a shortcut for ''jQuery'' namespace and it is possible to use full name instead. But to avoid conflicts with other libraries $ shortcut should is turned off by switching jQuery into non-conflict mode with ''jQuery.noConflict()'' call.  This is well explained in http://docs.jquery.com/Using_jQuery_with_Other_Libraries

However, you will see many blocks in Trac that use $ for jQuery. They do it in their local scope defined by nameless function (or closure):
{{{
(function($) { /* some code that uses $ */ })(jQuery)
}}}
There is a good description of closures and `(function(){})()` construct at http://ajaxian.com/archives/secrets-of-the-javascript-ninja-a-sneak-peak-for-ajaxians

==== $(document).ready() ====

To execute and modify DOM tree JavaScript function should usually wait until a page fully loads. With jQuery it looks like:
{{{
$(document).ready(function_name); 
}}}
In non-conflicting mode, code that executed in Trac on page startup is enveloped in closure and looks like:
{{{
jQuery(document).ready(function($) { ... }); 
}}}