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{{Deprecated|version=3.8}}
The use of jQuery in new code is strongly discouraged and is not generally accepted in new code. Specific exceptions to this rule are made on a case-by-case basis, generally when interfacing with legacy code which expects to be passed a jQuery object.

Moodle supports the use of native ES6-style modules and constructs since Moodle 3.8. These are transpiled into supported code.

{{Moodle 2.9}}

Before Moodle 2.9 we used [[YUI]] to write javascript in Moodle. As of Moodle 2.9 we are transitioning to jQuery and [[Javascript Modules]] because Yahoo has ceased all new development on YUI (http://yahooeng.tumblr.com/post/96098168666/important-announcement-regarding-yui).  

This page explains the recommended way to use jQuery in core and plugins, although other [[jQuery pre2.9|older]] methods of including jQuery will still work. 

== Why do we need JQuery? ==
'''We do not need jQuery and its use is discouraged'''. The following is legacy documentation and no longer current advice.

JQuery is useful for handling browser inconsistencies, and for utility functions that would otherwise be duplicated all over the code. Some particular things that JQuery is good at are:
* DOM Manipulations
* Promises ($.Deferred)
* Ajax

== How to use JQuery ==
As of Moodle 2.9, the recommended way to write javascript is in AMD Modules. For more information on writing AMD modules in Moodle see [[ Javascript Modules ]]. 

JQuery has been added as an AMD Module and is available to all AMD javascript. 

To make use of JQuery, either list it as a dependency of your module, or use a require call to load it. 

=== As a dependency of a module ===
<syntaxhighlight lang="php">
    define(['jquery'], function($) {
        // Private functions.
        var privateFunc = function(a) {
            // JQuery is available via $ if I want it
            return a + 1;
        };
    
        // Public functions.
        return {
            publicFunc: function(b) {
                // JQuery is available via $ if I want it
                return privateFunc(b) + 1;
            }
        }
    });
</syntaxhighlight>

=== With a require call ===
<syntaxhighlight lang="php">
    require(['jquery'], function($) {
        // JQuery is available via $
    });
    // JQuery is not in scope and cannot be used.
</syntaxhighlight>

== What about JQuery UI ? ==
JQuery UI is a separate project containing a library of reusable widgets that relies on JQuery. JQuery UI is available for plugins to use, but it should not be used in core code. 

The problems with JQuery UI are:
* It uses an entirely different themeing system for CSS that does not work well with Moodle themes
* It introduces CSS conflicts with bootstrap
* The widgets have some accessibility features - but only if used in a very specific way which is not well documented

Over time we will build up a library of widgets in core either by wrapping a suitable library or implementing from scratch.

If you STILL want to use JQuery UI in your plugin, it is available as an AMD module named 'jqueryui'.

<syntaxhighlight lang="php">
    require(['jquery', 'jqueryui'], function($, jqui) {
        // JQuery is available via $
        // JQuery UI is available via $.ui
    });
    // JQuery is not in scope and cannot be used.
    // JQuery UI is not in scope and cannot be used.
</syntaxhighlight>

{{Moodle 3.2}}
In Moodle 3.2 we upgraded jQuery to 3.1 and removed the jQuery migrate plugin. You should not have to change your code unless you have been ignoring jQuery deprecation notices for many many years (but it's recommended to test it in 3.2).

==See also==
* [[Javascript Modules]]
* [[Useful core Javascript modules]]
* [[jQuery pre2.9]]
* [http://jquery.com jQuery]
* [http://jqueryui.com jQuery User Interface]

[[Category:Javascript]]