From MoodleDocs

This feature has been marked as deprecated since Moodle 2.9

This document provides an brief overview of Moodle's use of YUI.

Note: As of Moodle 2.9 we are transitioning away from YUI to AMD modules. This transition will take a long time, but it is important because the YUI team have stopped all new development on the YUI library ( http://yahooeng.tumblr.com/post/96098168666/important-announcement-regarding-yui ). See Javascript Modules for more information.

Originally this transition suggested the use of jQuery, but since Moodle 3.8 the recommendation is to write Native Vanilla code in the ES2015 module style.

Moodle 2.4

Moodle 2.5

Moodle 2.6

Moodle 2.7

The Yahoo! User Interface (YUI) framework is a fast, powerful, modular, and well-documented framework with a powerful loading system.

The Basics

YUI is an extremely extensible, fast, modular, and powerful JavaScript framework with a very capable loading system. A number of modules are available for YUI providing a wide range of functionality to suit most situations. All of the core YUI modules are documented on their API. We are working to put together documentation for moodle's YUI modules too.

Since version 2.4, Moodle has included SimpleYUI to expose several features natively without requiring you to specify which features you wish to use. Prior to this a basic YUI was included. SimpleYUI loads a number of standard modules and makes them available on the global Y namespace. These include:

Whilst accessing the global Y variable will suffice for many uses, we highly recommend that you look at writing your code within a YUI module. It is also possible to use one of the other methods to include your JavaScript. These include:

  • inclusion of a javascript file (e.g. a file included by a theme); and
  • inclusion of a module.js file.

It is also possible to use JavaScript within a Database module - see the JavaScript template setting for further information.


YUI is extremely modular with different components, features, plugins, and tasks broken down into YUI Modules. When using YUI, you can choose which modules you wish to use and the YUI loader will go away and retrieve those modules, determining their dependencies automatically. This has the effect of separating out the load and execution phases of JavaScript component loading and also allows for asynchronous loading of the code. For a deeper dive on the benefits of this separation, it's well worth watching this video entitled YUI3 Below the Surface.

In order to benefit from these features, it is necessary to wrap your code in a registration function. This wrapper defines the name of the module, wraps the code in a closure to offer module sandboxing, and defines meta-data to inform the loader of any specific dependencies. A complete wrapper is shown below:

YUI.add('moodle-block_fruit-fruitbowl', function(Y) {
  // Your module code goes here.
}, '@VERSION@', {
  requires: ['panel']

Note: From Moodle 2.5, it is possible to write your modules in such a way that you do not have to explicitly specify write the YUI.add() wrapper.

To then make use of this code, you then have to use it. For example:

YUI().use('moodle-block_fruit-fruitbowl', function(Y) {
  // Use the class you defined earlier.

Documentation and further information

Other YUI documentation you may find useful:

We will soon be adding API Documentation for Moodle-specific YUI modules in addition to the core YUI library.


Some good books:

Useful tools

JavaScript authoring have moved along considerably in recent years, and we highly recommend that you look at using some of the available tools to help you in your development. Most of these tools are available through Node.js which is relatively trivial to install on most operating systems:


Shifter is a tool to help manage your YUI modules. It takes away some of the confusion associated with creating a YUI module (like the YUI.add line) and moves the metadata out of your module, and into a separate json file. This means that it can be picked up by Moodle to reduce the number of HTTP transactions through use of the YUI combo loader. Shifter also lints your code with jshint, and minifies your code too.

The upstream YUI project use a tool called Shifter to wrap up meta-data, rollup files, minify, and strip out debugging information from files. We will shortly be shifting to use of Shifter for core Moodle as it offers us many potential benefits.

Note: More information on the use of Shifter within Moodle is discussed at Javascript/Shifter.


Installation is relatively simple from the node.js Packaging Manager:

    npm install shifter@SUPPORTEDVERSION -g

For information on the current support version see Javascript/Shifter#Supported_version_of_Shifter


There are two ways to run shifter depending on your intended use.

During development, we recommend you run shifter in --watch mode. To do so, enter the src directory of the module you are working on and run:

cd lib/yui/src
shifter --watch

For more general use, you can run shifter across the whole of Moodle using --walk:

shifter --walk --recursive

...from your Moodle wwwroot.

Read more about shifter: https://moodle.org/mod/forum/discuss.php?d=217450


JSHint is a JSLint derivative for checking your code. This includes checking for errors and recommended stylistic approaches to writing JavaScript.

Since Moodle 2.5, a JSHint configuration is also included in the Moodle codebase to inform the tester of our preferences and recommendations.


Installation is relatively simple:

    npm install jshint -g


Many IDEs and editors will automatically detect if you have JSHint installed and pass your code through it for you, reporting any errors as you go.

To run jshint on the command line, simply pass it the file that you wish to check:

    jshint blocks/fruit/yui/fruitbowl/fruitbowl.js


There's a variety of documentation on JSHint and the error messages it returns. Start off with the jshint website:


YUIDoc is a documentation system. It can work with any type of code, but is designed with JavaScript in mind. It's the documentation system used to create the YUI core API documentation, and will soon be used to create API documentation for Moodle-specific YUI modules in core.


Installation is relatively simple:

    npm install yuidocjs -g


To run yuidoc across the entirety of Moodle JavaScript, from the root directory run:


Whilst writing your documentation, you may also like to run yuidoc in server mode. See the --server option for help on how to do this.


There's a variety of documentation on JSHint and the error messages it returns. Start off with the jshint website:

Moodle Settings for Javascript Development

The following settings will ensure that the js loaded by your browser is relatively readable.

Make sure that :

  • your Development / Debugging / Debug messages is set to "Developer : Extra Debug Moodle Messages ...." - Moodle will then use the debug non-minified and thus more readable YUI 2 and YUI 3 library files.
  • You will probably want to change some of the settings at "Home / Site administration / Appearance / AJAX and Javascript" :
    • YUI combo loading - you probably want to turn this off so that files are not combined.
    • Javascript caching and compressing - turn this off so that your custom JS code is not minified.
    • Check the other settings on this page to see that they are as you would expect them to be.

You might want to add the following code to your config.php file when developing or debugging javascript code:

// For javascript development or debugging.
$CFG->cachejs = false;
$CFG->yuicomboloading = false;
$CFG->yuiloglevel = 'debug';
$CFG->debug = 32767;

See Also