[lhc/web/wiklou.git] / resources / src / mediawiki / mediawiki.js

/**
 * Base library for MediaWiki.
 *
 * Exposed globally as `mediaWiki` with `mw` as shortcut.
 *
 * @class mw
 * @alternateClassName mediaWiki
 * @singleton
 */
( function ( $ ) {
        'use strict';

        var mw,
                hasOwn = Object.prototype.hasOwnProperty,
                slice = Array.prototype.slice,
                trackCallbacks = $.Callbacks( 'memory' ),
                trackQueue = [];

        /**
         * Log a message to window.console, if possible.
         *
         * Useful to force logging of some  errors that are otherwise hard to detect (i.e., this logs
         * also in production mode). Gets console references in each invocation instead of caching the
         * reference, so that debugging tools loaded later are supported (e.g. Firebug Lite in IE).
         *
         * @private
         * @method log_
         * @param {string} msg Text for the log entry.
         * @param {Error} [e]
         */
        function log( msg, e ) {
                var console = window.console;
                if ( console && console.log ) {
                        console.log( msg );
                        // If we have an exception object, log it to the error channel to trigger a
                        // proper stacktraces in browsers that support it. No fallback as we have no browsers
                        // that don't support error(), but do support log().
                        if ( e && console.error ) {
                                console.error( String( e ), e );
                        }
                }
        }

        /**
         * Create an object that can be read from or written to from methods that allow
         * interaction both with single and multiple properties at once.
         *
         *     @example
         *
         *     var collection, query, results;
         *
         *     // Create your address book
         *     collection = new mw.Map();
         *
         *     // This data could be coming from an external source (eg. API/AJAX)
         *     collection.set( {
         *         'John Doe': 'john@example.org',
         *         'Jane Doe': 'jane@example.org',
         *         'George van Halen': 'gvanhalen@example.org'
         *     } );
         *
         *     wanted = ['John Doe', 'Jane Doe', 'Daniel Jackson'];
         *
         *     // You can detect missing keys first
         *     if ( !collection.exists( wanted ) ) {
         *         // One or more are missing (in this case: "Daniel Jackson")
         *         mw.log( 'One or more names were not found in your address book' );
         *     }
         *
         *     // Or just let it give you what it can. Optionally fill in from a default.
         *     results = collection.get( wanted, 'nobody@example.com' );
         *     mw.log( results['Jane Doe'] ); // "jane@example.org"
         *     mw.log( results['Daniel Jackson'] ); // "nobody@example.com"
         *
         * @class mw.Map
         *
         * @constructor
         * @param {Object|boolean} [values] The value-baring object to be mapped. Defaults to an
         *  empty object.
         *  For backwards-compatibility with mw.config, this can also be `true` in which case values
         *  are copied to the Window object as global variables (T72470). Values are copied in
         *  one direction only. Changes to globals are not reflected in the map.
         */
        function Map( values ) {
                if ( values === true ) {
                        this.values = {};

                        // Override #set to also set the global variable
                        this.set = function ( selection, value ) {
                                var s;

                                if ( $.isPlainObject( selection ) ) {
                                        for ( s in selection ) {
                                                setGlobalMapValue( this, s, selection[s] );
                                        }
                                        return true;
                                }
                                if ( typeof selection === 'string' && arguments.length ) {
                                        setGlobalMapValue( this, selection, value );
                                        return true;
                                }
                                return false;
                        };

                        return;
                }

                this.values = values || {};
        }

        /**
         * Alias property to the global object.
         *
         * @private
         * @static
         * @param {mw.Map} map
         * @param {string} key
         * @param {Mixed} value
         */
        function setGlobalMapValue( map, key, value ) {
                map.values[key] = value;
                mw.log.deprecate(
                        window,
                        key,
                        value,
                        // Deprecation notice for mw.config globals (T58550, T72470)
                        map === mw.config && 'Use mw.config instead.'
                );
        }

        Map.prototype = {
                /**
                 * Get the value of one or more keys.
                 *
                 * If called with no arguments, all values are returned.
                 *
                 * @param {string|Array} [selection] Key or array of keys to retrieve values for.
                 * @param {Mixed} [fallback=null] Value for keys that don't exist.
                 * @return {Mixed|Object| null} If selection was a string, returns the value,
                 *  If selection was an array, returns an object of key/values.
                 *  If no selection is passed, the 'values' container is returned. (Beware that,
                 *  as is the default in JavaScript, the object is returned by reference.)
                 */
                get: function ( selection, fallback ) {
                        var results, i;
                        // If we only do this in the `return` block, it'll fail for the
                        // call to get() from the mutli-selection block.
                        fallback = arguments.length > 1 ? fallback : null;

                        if ( $.isArray( selection ) ) {
                                selection = slice.call( selection );
                                results = {};
                                for ( i = 0; i < selection.length; i++ ) {
                                        results[selection[i]] = this.get( selection[i], fallback );
                                }
                                return results;
                        }

                        if ( typeof selection === 'string' ) {
                                if ( !hasOwn.call( this.values, selection ) ) {
                                        return fallback;
                                }
                                return this.values[selection];
                        }

                        if ( selection === undefined ) {
                                return this.values;
                        }

                        // Invalid selection key
                        return null;
                },

                /**
                 * Set one or more key/value pairs.
                 *
                 * @param {string|Object} selection Key to set value for, or object mapping keys to values
                 * @param {Mixed} [value] Value to set (optional, only in use when key is a string)
                 * @return {boolean} True on success, false on failure
                 */
                set: function ( selection, value ) {
                        var s;

                        if ( $.isPlainObject( selection ) ) {
                                for ( s in selection ) {
                                        this.values[s] = selection[s];
                                }
                                return true;
                        }
                        if ( typeof selection === 'string' && arguments.length > 1 ) {
                                this.values[selection] = value;
                                return true;
                        }
                        return false;
                },

                /**
                 * Check if one or more keys exist.
                 *
                 * @param {Mixed} selection Key or array of keys to check
                 * @return {boolean} True if the key(s) exist
                 */
                exists: function ( selection ) {
                        var s;

                        if ( $.isArray( selection ) ) {
                                for ( s = 0; s < selection.length; s++ ) {
                                        if ( typeof selection[s] !== 'string' || !hasOwn.call( this.values, selection[s] ) ) {
                                                return false;
                                        }
                                }
                                return true;
                        }
                        return typeof selection === 'string' && hasOwn.call( this.values, selection );
                }
        };

        /**
         * Object constructor for messages.
         *
         * Similar to the Message class in MediaWiki PHP.
         *
         * Format defaults to 'text'.
         *
         *     @example
         *
         *     var obj, str;
         *     mw.messages.set( {
         *         'hello': 'Hello world',
         *         'hello-user': 'Hello, $1!',
         *         'welcome-user': 'Welcome back to $2, $1! Last visit by $1: $3'
         *     } );
         *
         *     obj = new mw.Message( mw.messages, 'hello' );
         *     mw.log( obj.text() );
         *     // Hello world
         *
         *     obj = new mw.Message( mw.messages, 'hello-user', [ 'John Doe' ] );
         *     mw.log( obj.text() );
         *     // Hello, John Doe!
         *
         *     obj = new mw.Message( mw.messages, 'welcome-user', [ 'John Doe', 'Wikipedia', '2 hours ago' ] );
         *     mw.log( obj.text() );
         *     // Welcome back to Wikipedia, John Doe! Last visit by John Doe: 2 hours ago
         *
         *     // Using mw.message shortcut
         *     obj = mw.message( 'hello-user', 'John Doe' );
         *     mw.log( obj.text() );
         *     // Hello, John Doe!
         *
         *     // Using mw.msg shortcut
         *     str = mw.msg( 'hello-user', 'John Doe' );
         *     mw.log( str );
         *     // Hello, John Doe!
         *
         *     // Different formats
         *     obj = new mw.Message( mw.messages, 'hello-user', [ 'John "Wiki" <3 Doe' ] );
         *
         *     obj.format = 'text';
         *     str = obj.toString();
         *     // Same as:
         *     str = obj.text();
         *
         *     mw.log( str );
         *     // Hello, John "Wiki" <3 Doe!
         *
         *     mw.log( obj.escaped() );
         *     // Hello, John &quot;Wiki&quot; &lt;3 Doe!
         *
         * @class mw.Message
         *
         * @constructor
         * @param {mw.Map} map Message store
         * @param {string} key
         * @param {Array} [parameters]
         */
        function Message( map, key, parameters ) {
                this.format = 'text';
                this.map = map;
                this.key = key;
                this.parameters = parameters === undefined ? [] : slice.call( parameters );
                return this;
        }

        Message.prototype = {
                /**
                 * Get parsed contents of the message.
                 *
                 * The default parser does simple $N replacements and nothing else.
                 * This may be overridden to provide a more complex message parser.
                 * The primary override is in the mediawiki.jqueryMsg module.
                 *
                 * This function will not be called for nonexistent messages.
                 *
                 * @return {string} Parsed message
                 */
                parser: function () {
                        return mw.format.apply( null, [ this.map.get( this.key ) ].concat( this.parameters ) );
                },

                /**
                 * Add (does not replace) parameters for `N$` placeholder values.
                 *
                 * @param {Array} parameters
                 * @chainable
                 */
                params: function ( parameters ) {
                        var i;
                        for ( i = 0; i < parameters.length; i += 1 ) {
                                this.parameters.push( parameters[i] );
                        }
                        return this;
                },

                /**
                 * Convert message object to its string form based on current format.
                 *
                 * @return {string} Message as a string in the current form, or `<key>` if key
                 *  does not exist.
                 */
                toString: function () {
                        var text;

                        if ( !this.exists() ) {
                                // Use <key> as text if key does not exist
                                if ( this.format === 'escaped' || this.format === 'parse' ) {
                                        // format 'escaped' and 'parse' need to have the brackets and key html escaped
                                        return mw.html.escape( '<' + this.key + '>' );
                                }
                                return '<' + this.key + '>';
                        }

                        if ( this.format === 'plain' || this.format === 'text' || this.format === 'parse' ) {
                                text = this.parser();
                        }

                        if ( this.format === 'escaped' ) {
                                text = this.parser();
                                text = mw.html.escape( text );
                        }

                        return text;
                },

                /**
                 * Change format to 'parse' and convert message to string
                 *
                 * If jqueryMsg is loaded, this parses the message text from wikitext
                 * (where supported) to HTML
                 *
                 * Otherwise, it is equivalent to plain.
                 *
                 * @return {string} String form of parsed message
                 */
                parse: function () {
                        this.format = 'parse';
                        return this.toString();
                },

                /**
                 * Change format to 'plain' and convert message to string
                 *
                 * This substitutes parameters, but otherwise does not change the
                 * message text.
                 *
                 * @return {string} String form of plain message
                 */
                plain: function () {
                        this.format = 'plain';
                        return this.toString();
                },

                /**
                 * Change format to 'text' and convert message to string
                 *
                 * If jqueryMsg is loaded, {{-transformation is done where supported
                 * (such as {{plural:}}, {{gender:}}, {{int:}}).
                 *
                 * Otherwise, it is equivalent to plain
                 *
                 * @return {string} String form of text message
                 */
                text: function () {
                        this.format = 'text';
                        return this.toString();
                },

                /**
                 * Change the format to 'escaped' and convert message to string
                 *
                 * This is equivalent to using the 'text' format (see #text), then
                 * HTML-escaping the output.
                 *
                 * @return {string} String form of html escaped message
                 */
                escaped: function () {
                        this.format = 'escaped';
                        return this.toString();
                },

                /**
                 * Check if a message exists
                 *
                 * @see mw.Map#exists
                 * @return {boolean}
                 */
                exists: function () {
                        return this.map.exists( this.key );
                }
        };

        /**
         * @class mw
         */
        mw = {

                /**
                 * Get the current time, measured in milliseconds since January 1, 1970 (UTC).
                 *
                 * On browsers that implement the Navigation Timing API, this function will produce floating-point
                 * values with microsecond precision that are guaranteed to be monotonic. On all other browsers,
                 * it will fall back to using `Date`.
                 *
                 * @return {number} Current time
                 */
                now: ( function () {
                        var perf = window.performance,
                                navStart = perf && perf.timing && perf.timing.navigationStart;
                        return navStart && typeof perf.now === 'function' ?
                                function () { return navStart + perf.now(); } :
                                function () { return +new Date(); };
                }() ),

                /**
                 * Format a string. Replace $1, $2 ... $N with positional arguments.
                 *
                 * Used by Message#parser().
                 *
                 * @since 1.25
                 * @param {string} fmt Format string
                 * @param {Mixed...} parameters Values for $N replacements
                 * @return {string} Formatted string
                 */
                format: function ( formatString ) {
                        var parameters = slice.call( arguments, 1 );
                        return formatString.replace( /\$(\d+)/g, function ( str, match ) {
                                var index = parseInt( match, 10 ) - 1;
                                return parameters[index] !== undefined ? parameters[index] : '$' + match;
                        } );
                },

                /**
                 * Track an analytic event.
                 *
                 * This method provides a generic means for MediaWiki JavaScript code to capture state
                 * information for analysis. Each logged event specifies a string topic name that describes
                 * the kind of event that it is. Topic names consist of dot-separated path components,
                 * arranged from most general to most specific. Each path component should have a clear and
                 * well-defined purpose.
                 *
                 * Data handlers are registered via `mw.trackSubscribe`, and receive the full set of
                 * events that match their subcription, including those that fired before the handler was
                 * bound.
                 *
                 * @param {string} topic Topic name
                 * @param {Object} [data] Data describing the event, encoded as an object
                 */
                track: function ( topic, data ) {
                        trackQueue.push( { topic: topic, timeStamp: mw.now(), data: data } );
                        trackCallbacks.fire( trackQueue );
                },

                /**
                 * Register a handler for subset of analytic events, specified by topic.
                 *
                 * Handlers will be called once for each tracked event, including any events that fired before the
                 * handler was registered; 'this' is set to a plain object with a 'timeStamp' property indicating
                 * the exact time at which the event fired, a string 'topic' property naming the event, and a
                 * 'data' property which is an object of event-specific data. The event topic and event data are
                 * also passed to the callback as the first and second arguments, respectively.
                 *
                 * @param {string} topic Handle events whose name starts with this string prefix
                 * @param {Function} callback Handler to call for each matching tracked event
                 * @param {string} callback.topic
                 * @param {Object} [callback.data]
                 */
                trackSubscribe: function ( topic, callback ) {
                        var seen = 0;

                        trackCallbacks.add( function ( trackQueue ) {
                                var event;
                                for ( ; seen < trackQueue.length; seen++ ) {
                                        event = trackQueue[ seen ];
                                        if ( event.topic.indexOf( topic ) === 0 ) {
                                                callback.call( event, event.topic, event.data );
                                        }
                                }
                        } );
                },

                // Expose Map constructor
                Map: Map,

                // Expose Message constructor
                Message: Message,

                /**
                 * Map of configuration values.
                 *
                 * Check out [the complete list of configuration values](https://www.mediawiki.org/wiki/Manual:Interface/JavaScript#mw.config)
                 * on mediawiki.org.
                 *
                 * If `$wgLegacyJavaScriptGlobals` is true, this Map will add its values to the
                 * global `window` object.
                 *
                 * @property {mw.Map} config
                 */
                // Dummy placeholder later assigned in ResourceLoaderStartUpModule
                config: null,

                /**
                 * Empty object that plugins can be installed in.
                 *
                 * @property
                 */
                libs: {},

                /**
                 * Access container for deprecated functionality that can be moved from
                 * from their legacy location and attached to this object (e.g. a global
                 * function that is deprecated and as stop-gap can be exposed through here).
                 *
                 * This was reserved for future use but never ended up being used.
                 *
                 * @deprecated since 1.22 Let deprecated identifiers keep their original name
                 *  and use mw.log#deprecate to create an access container for tracking.
                 * @property
                 */
                legacy: {},

                /**
                 * Store for messages.
                 *
                 * @property {mw.Map}
                 */
                messages: new Map(),

                /**
                 * Store for templates associated with a module.
                 *
                 * @property {mw.Map}
                 */
                templates: new Map(),

                /**
                 * Get a message object.
                 *
                 * Shorcut for `new mw.Message( mw.messages, key, parameters )`.
                 *
                 * @see mw.Message
                 * @param {string} key Key of message to get
                 * @param {Mixed...} parameters Values for $N replacements
                 * @return {mw.Message}
                 */
                message: function ( key ) {
                        var parameters = slice.call( arguments, 1 );
                        return new Message( mw.messages, key, parameters );
                },

                /**
                 * Get a message string using the (default) 'text' format.
                 *
                 * Shortcut for `mw.message( key, parameters... ).text()`.
                 *
                 * @see mw.Message
                 * @param {string} key Key of message to get
                 * @param {Mixed...} parameters Values for $N replacements
                 * @return {string}
                 */
                msg: function () {
                        return mw.message.apply( mw.message, arguments ).toString();
                },

                /**
                 * Dummy placeholder for {@link mw.log}
                 * @method
                 */
                log: ( function () {
                        // Also update the restoration of methods in mediawiki.log.js
                        // when adding or removing methods here.
                        var log = function () {};

                        /**
                         * @class mw.log
                         * @singleton
                         */

                        /**
                         * Write a message the console's warning channel.
                         * Also logs a stacktrace for easier debugging.
                         * Actions not supported by the browser console are silently ignored.
                         *
                         * @param {string...} msg Messages to output to console
                         */
                        log.warn = function () {
                                var console = window.console;
                                if ( console && console.warn && console.warn.apply ) {
                                        console.warn.apply( console, arguments );
                                        if ( console.trace ) {
                                                console.trace();
                                        }
                                }
                        };

                        /**
                         * Create a property in a host object that, when accessed, will produce
                         * a deprecation warning in the console with backtrace.
                         *
                         * @param {Object} obj Host object of deprecated property
                         * @param {string} key Name of property to create in `obj`
                         * @param {Mixed} val The value this property should return when accessed
                         * @param {string} [msg] Optional text to include in the deprecation message
                         */
                        log.deprecate = !Object.defineProperty ? function ( obj, key, val ) {
                                obj[key] = val;
                        } : function ( obj, key, val, msg ) {
                                msg = 'Use of "' + key + '" is deprecated.' + ( msg ? ( ' ' + msg ) : '' );
                                // Support: IE8
                                // Can throw on Object.defineProperty.
                                try {
                                        Object.defineProperty( obj, key, {
                                                configurable: true,
                                                enumerable: true,
                                                get: function () {
                                                        mw.track( 'mw.deprecate', key );
                                                        mw.log.warn( msg );
                                                        return val;
                                                },
                                                set: function ( newVal ) {
                                                        mw.track( 'mw.deprecate', key );
                                                        mw.log.warn( msg );
                                                        val = newVal;
                                                }
                                        } );
                                } catch ( err ) {
                                        // Fallback to creating a copy of the value to the object.
                                        obj[key] = val;
                                }
                        };

                        return log;
                }() ),

                /**
                 * Client for ResourceLoader server end point.
                 *
                 * This client is in charge of maintaining the module registry and state
                 * machine, initiating network (batch) requests for loading modules, as
                 * well as dependency resolution and execution of source code.
                 *
                 * For more information, refer to
                 * <https://www.mediawiki.org/wiki/ResourceLoader/Features>
                 *
                 * @class mw.loader
                 * @singleton
                 */
                loader: ( function () {

                        /**
                         * Mapping of registered modules.
                         *
                         * See #implement for exact details on support for script, style and messages.
                         *
                         * Format:
                         *
                         *     {
                         *         'moduleName': {
                         *             // From startup mdoule
                         *             'version': ############## (unix timestamp)
                         *             'dependencies': ['required.foo', 'bar.also', ...], (or) function () {}
                         *             'group': 'somegroup', (or) null
                         *             'source': 'local', (or) 'anotherwiki'
                         *             'skip': 'return !!window.Example', (or) null
                         *             'state': 'registered', 'loaded', 'loading', 'ready', 'error', or 'missing'
                         *
                         *             // Added during implementation
                         *             'skipped': true
                         *             'script': ...
                         *             'style': ...
                         *             'messages': { 'key': 'value' }
                         *         }
                         *     }
                         *
                         * @property
                         * @private
                         */
                        var registry = {},
                                // Mapping of sources, keyed by source-id, values are strings.
                                //
                                // Format:
                                //
                                //     {
                                //         'sourceId': 'http://example.org/w/load.php'
                                //     }
                                //
                                sources = {},

                                // List of modules which will be loaded as when ready
                                batch = [],

                                // List of modules to be loaded
                                queue = [],

                                // List of callback functions waiting for modules to be ready to be called
                                jobs = [],

                                // Selector cache for the marker element. Use getMarker() to get/use the marker!
                                $marker = null,

                                // Buffer for #addEmbeddedCSS
                                cssBuffer = '',

                                // Callbacks for #addEmbeddedCSS
                                cssCallbacks = $.Callbacks();

                        function getMarker() {
                                if ( !$marker ) {
                                        // Cache
                                        $marker = $( 'meta[name="ResourceLoaderDynamicStyles"]' );
                                        if ( !$marker.length ) {
                                                mw.log( 'No <meta name="ResourceLoaderDynamicStyles"> found, inserting dynamically' );
                                                $marker = $( '<meta>' ).attr( 'name', 'ResourceLoaderDynamicStyles' ).appendTo( 'head' );
                                        }
                                }
                                return $marker;
                        }

                        /**
                         * Create a new style element and add it to the DOM.
                         *
                         * @private
                         * @param {string} text CSS text
                         * @param {HTMLElement|jQuery} [nextnode=document.head] The element where the style tag
                         *  should be inserted before
                         * @return {HTMLElement} Reference to the created style element
                         */
                        function newStyleTag( text, nextnode ) {
                                var s = document.createElement( 'style' );
                                // Support: IE
                                // Must attach to document before setting cssText (bug 33305)
                                if ( nextnode ) {
                                        $( nextnode ).before( s );
                                } else {
                                        document.getElementsByTagName( 'head' )[0].appendChild( s );
                                }
                                if ( s.styleSheet ) {
                                        // Support: IE6-10
                                        // Old IE ignores appended text nodes, access stylesheet directly.
                                        s.styleSheet.cssText = text;
                                } else {
                                        // Standard behaviour
                                        s.appendChild( document.createTextNode( text ) );
                                }
                                return s;
                        }

                        /**
                         * Check whether given styles are safe to to a stylesheet.
                         *
                         * @private
                         * @param {string} cssText
                         * @return {boolean} False if a new one must be created.
                         */
                        function canExpandStylesheetWith( cssText ) {
                                // Makes sure that cssText containing `@import`
                                // rules will end up in a new stylesheet (as those only work when
                                // placed at the start of a stylesheet; bug 35562).
                                return cssText.indexOf( '@import' ) === -1;
                        }

                        /**
                         * Add a bit of CSS text to the current browser page.
                         *
                         * The CSS will be appended to an existing ResourceLoader-created `<style>` tag
                         * or create a new one based on whether the given `cssText` is safe for extension.
                         *
                         * @param {string} [cssText=cssBuffer] If called without cssText,
                         *  the internal buffer will be inserted instead.
                         * @param {Function} [callback]
                         */
                        function addEmbeddedCSS( cssText, callback ) {
                                var $style, styleEl;

                                if ( callback ) {
                                        cssCallbacks.add( callback );
                                }

                                // Yield once before inserting the <style> tag. There are likely
                                // more calls coming up which we can combine this way.
                                // Appending a stylesheet and waiting for the browser to repaint
                                // is fairly expensive, this reduces that (bug 45810)
                                if ( cssText ) {
                                        // Be careful not to extend the buffer with css that needs a new stylesheet
                                        if ( !cssBuffer || canExpandStylesheetWith( cssText ) ) {
                                                // Linebreak for somewhat distinguishable sections
                                                // (the rl-cachekey comment separating each)
                                                cssBuffer += '\n' + cssText;
                                                // TODO: Use requestAnimationFrame in the future which will
                                                // perform even better by not injecting styles while the browser
                                                // is painting.
                                                setTimeout( function () {
                                                        // Can't pass addEmbeddedCSS to setTimeout directly because Firefox
                                                        // (below version 13) has the non-standard behaviour of passing a
                                                        // numerical "lateness" value as first argument to this callback
                                                        // http://benalman.com/news/2009/07/the-mysterious-firefox-settime/
                                                        addEmbeddedCSS();
                                                } );
                                                return;
                                        }

                                // This is a delayed call and we got a buffer still
                                } else if ( cssBuffer ) {
                                        cssText = cssBuffer;
                                        cssBuffer = '';

                                } else {
                                        // This is a delayed call, but buffer was already cleared by
                                        // another delayed call.
                                        return;
                                }

                                // By default, always create a new <style>. Appending text to a <style>
                                // tag is bad as it means the contents have to be re-parsed (bug 45810).
                                //
                                // Except, of course, in IE 9 and below. In there we default to re-using and
                                // appending to a <style> tag due to the IE stylesheet limit (bug 31676).
                                if ( 'documentMode' in document && document.documentMode <= 9 ) {

                                        $style = getMarker().prev();
                                        // Verify that the element before the marker actually is a
                                        // <style> tag and one that came from ResourceLoader
                                        // (not some other style tag or even a `<meta>` or `<script>`).
                                        if ( $style.data( 'ResourceLoaderDynamicStyleTag' ) === true ) {
                                                // There's already a dynamic <style> tag present and
                                                // canExpandStylesheetWith() gave a green light to append more to it.
                                                styleEl = $style.get( 0 );
                                                // Support: IE6-10
                                                if ( styleEl.styleSheet ) {
                                                        try {
                                                                styleEl.styleSheet.cssText += cssText;
                                                        } catch ( e ) {
                                                                log( 'Stylesheet error', e );
                                                        }
                                                } else {
                                                        styleEl.appendChild( document.createTextNode( cssText ) );
                                                }
                                                cssCallbacks.fire().empty();
                                                return;
                                        }
                                }

                                $( newStyleTag( cssText, getMarker() ) ).data( 'ResourceLoaderDynamicStyleTag', true );

                                cssCallbacks.fire().empty();
                        }

                        /**
                         * Zero-pad three numbers.
                         *
                         * @private
                         * @param {number} a
                         * @param {number} b
                         * @param {number} c
                         * @return {string}
                         */
                        function pad( a, b, c ) {
                                return [
                                        a < 10 ? '0' + a : a,
                                        b < 10 ? '0' + b : b,
                                        c < 10 ? '0' + c : c
                                ].join( '' );
                        }

                        /**
                         * Convert UNIX timestamp to ISO8601 format.
                         *
                         * @private
                         * @param {number} timestamp UNIX timestamp
                         */
                        function formatVersionNumber( timestamp ) {
                                var     d = new Date();
                                d.setTime( timestamp * 1000 );
                                return [
                                        pad( d.getUTCFullYear(), d.getUTCMonth() + 1, d.getUTCDate() ),
                                        'T',
                                        pad( d.getUTCHours(), d.getUTCMinutes(), d.getUTCSeconds() ),
                                        'Z'
                                ].join( '' );
                        }

                        /**
                         * Resolve dependencies and detect circular references.
                         *
                         * @private
                         * @param {string} module Name of the top-level module whose dependencies shall be
                         *  resolved and sorted.
                         * @param {Array} resolved Returns a topological sort of the given module and its
                         *  dependencies, such that later modules depend on earlier modules. The array
                         *  contains the module names. If the array contains already some module names,
                         *  this function appends its result to the pre-existing array.
                         * @param {Object} [unresolved] Hash used to track the current dependency
                         *  chain; used to report loops in the dependency graph.
                         * @throws {Error} If any unregistered module or a dependency loop is encountered
                         */
                        function sortDependencies( module, resolved, unresolved ) {
                                var n, deps, len, skip;

                                if ( !hasOwn.call( registry, module ) ) {
                                        throw new Error( 'Unknown dependency: ' + module );
                                }

                                if ( registry[module].skip !== null ) {
                                        /*jshint evil:true */
                                        skip = new Function( registry[module].skip );
                                        registry[module].skip = null;
                                        if ( skip() ) {
                                                registry[module].skipped = true;
                                                registry[module].dependencies = [];
                                                registry[module].state = 'ready';
                                                handlePending( module );
                                                return;
                                        }
                                }

                                // Resolves dynamic loader function and replaces it with its own results
                                if ( $.isFunction( registry[module].dependencies ) ) {
                                        registry[module].dependencies = registry[module].dependencies();
                                        // Ensures the module's dependencies are always in an array
                                        if ( typeof registry[module].dependencies !== 'object' ) {
                                                registry[module].dependencies = [registry[module].dependencies];
                                        }
                                }
                                if ( $.inArray( module, resolved ) !== -1 ) {
                                        // Module already resolved; nothing to do
                                        return;
                                }
                                // Create unresolved if not passed in
                                if ( !unresolved ) {
                                        unresolved = {};
                                }
                                // Tracks down dependencies
                                deps = registry[module].dependencies;
                                len = deps.length;
                                for ( n = 0; n < len; n += 1 ) {
                                        if ( $.inArray( deps[n], resolved ) === -1 ) {
                                                if ( unresolved[deps[n]] ) {
                                                        throw new Error(
                                                                'Circular reference detected: ' + module +
                                                                ' -> ' + deps[n]
                                                        );
                                                }

                                                // Add to unresolved
                                                unresolved[module] = true;
                                                sortDependencies( deps[n], resolved, unresolved );
                                                delete unresolved[module];
                                        }
                                }
                                resolved[resolved.length] = module;
                        }

                        /**
                         * Get a list of module names that a module depends on in their proper dependency
                         * order.
                         *
                         * @private
                         * @param {string} module Module name or array of string module names
                         * @return {Array} List of dependencies, including 'module'.
                         * @throws {Error} If circular reference is detected
                         */
                        function resolve( module ) {
                                var m, resolved;

                                // Allow calling with an array of module names
                                if ( $.isArray( module ) ) {
                                        resolved = [];
                                        for ( m = 0; m < module.length; m += 1 ) {
                                                sortDependencies( module[m], resolved );
                                        }
                                        return resolved;
                                }

                                if ( typeof module === 'string' ) {
                                        resolved = [];
                                        sortDependencies( module, resolved );
                                        return resolved;
                                }

                                throw new Error( 'Invalid module argument: ' + module );
                        }

                        /**
                         * Narrow down a list of module names to those matching a specific
                         * state (see #registry for a list of valid states).
                         *
                         * One can also filter for 'unregistered', which will return the
                         * modules names that don't have a registry entry.
                         *
                         * @private
                         * @param {string|string[]} states Module states to filter by
                         * @param {Array} [modules] List of module names to filter (optional, by default the
                         * entire registry is used)
                         * @return {Array} List of filtered module names
                         */
                        function filter( states, modules ) {
                                var list, module, s, m;

                                // Allow states to be given as a string
                                if ( typeof states === 'string' ) {
                                        states = [states];
                                }
                                // If called without a list of modules, build and use a list of all modules
                                list = [];
                                if ( modules === undefined ) {
                                        modules = [];
                                        for ( module in registry ) {
                                                modules[modules.length] = module;
                                        }
                                }
                                // Build a list of modules which are in one of the specified states
                                for ( s = 0; s < states.length; s += 1 ) {
                                        for ( m = 0; m < modules.length; m += 1 ) {
                                                if ( !hasOwn.call( registry, modules[m] ) ) {
                                                        // Module does not exist
                                                        if ( states[s] === 'unregistered' ) {
                                                                // OK, undefined
                                                                list[list.length] = modules[m];
                                                        }
                                                } else {
                                                        // Module exists, check state
                                                        if ( registry[modules[m]].state === states[s] ) {
                                                                // OK, correct state
                                                                list[list.length] = modules[m];
                                                        }
                                                }
                                        }
                                }
                                return list;
                        }

                        /**
                         * Determine whether all dependencies are in state 'ready', which means we may
                         * execute the module or job now.
                         *
                         * @private
                         * @param {Array} dependencies Dependencies (module names) to be checked.
                         * @return {boolean} True if all dependencies are in state 'ready', false otherwise
                         */
                        function allReady( dependencies ) {
                                return filter( 'ready', dependencies ).length === dependencies.length;
                        }

                        /**
                         * A module has entered state 'ready', 'error', or 'missing'. Automatically update
                         * pending jobs and modules that depend upon this module. If the given module failed,
                         * propagate the 'error' state up the dependency tree. Otherwise, go ahead an execute
                         * all jobs/modules now having their dependencies satisfied.
                         *
                         * Jobs that depend on a failed module, will have their error callback ran (if any).
                         *
                         * @private
                         * @param {string} module Name of module that entered one of the states 'ready', 'error', or 'missing'.
                         */
                        function handlePending( module ) {
                                var j, job, hasErrors, m, stateChange;

                                if ( $.inArray( registry[module].state, ['error', 'missing'] ) !== -1 ) {
                                        // If the current module failed, mark all dependent modules also as failed.
                                        // Iterate until steady-state to propagate the error state upwards in the
                                        // dependency tree.
                                        do {
                                                stateChange = false;
                                                for ( m in registry ) {
                                                        if ( $.inArray( registry[m].state, ['error', 'missing'] ) === -1 ) {
                                                                if ( filter( ['error', 'missing'], registry[m].dependencies ).length ) {
                                                                        registry[m].state = 'error';
                                                                        stateChange = true;
                                                                }
                                                        }
                                                }
                                        } while ( stateChange );
                                }

                                // Execute all jobs whose dependencies are either all satisfied or contain at least one failed module.
                                for ( j = 0; j < jobs.length; j += 1 ) {
                                        hasErrors = filter( ['error', 'missing'], jobs[j].dependencies ).length > 0;
                                        if ( hasErrors || allReady( jobs[j].dependencies ) ) {
                                                // All dependencies satisfied, or some have errors
                                                job = jobs[j];
                                                jobs.splice( j, 1 );
                                                j -= 1;
                                                try {
                                                        if ( hasErrors ) {
                                                                if ( $.isFunction( job.error ) ) {
                                                                        job.error( new Error( 'Module ' + module + ' has failed dependencies' ), [module] );
                                                                }
                                                        } else {
                                                                if ( $.isFunction( job.ready ) ) {
                                                                        job.ready();
                                                                }
                                                        }
                                                } catch ( e ) {
                                                        // A user-defined callback raised an exception.
                                                        // Swallow it to protect our state machine!
                                                        log( 'Exception thrown by user callback', e );
                                                }
                                        }
                                }

                                if ( registry[module].state === 'ready' ) {
                                        // The current module became 'ready'. Set it in the module store, and recursively execute all
                                        // dependent modules that are loaded and now have all dependencies satisfied.
                                        mw.loader.store.set( module, registry[module] );
                                        for ( m in registry ) {
                                                if ( registry[m].state === 'loaded' && allReady( registry[m].dependencies ) ) {
                                                        execute( m );
                                                }
                                        }
                                }
                        }

                        /**
                         * Adds a script tag to the DOM, either using document.write or low-level DOM manipulation,
                         * depending on whether document-ready has occurred yet and whether we are in async mode.
                         *
                         * @private
                         * @param {string} src URL to script, will be used as the src attribute in the script tag
                         * @param {Function} [callback] Callback which will be run when the script is done
                         * @param {boolean} [async=false] Whether to load modules asynchronously.
                         *  Ignored (and defaulted to `true`) if the document-ready event has already occurred.
                         */
                        function addScript( src, callback, async ) {
                                // Using isReady directly instead of storing it locally from a $().ready callback (bug 31895)
                                if ( $.isReady || async ) {
                                        $.ajax( {
                                                url: src,
                                                dataType: 'script',
                                                // Force jQuery behaviour to be for crossDomain. Otherwise jQuery would use
                                                // XHR for a same domain request instead of <script>, which changes the request
                                                // headers (potentially missing a cache hit), and reduces caching in general
                                                // since browsers cache XHR much less (if at all). And XHR means we retreive
                                                // text, so we'd need to $.globalEval, which then messes up line numbers.
                                                crossDomain: true,
                                                cache: true,
                                                async: true
                                        } ).always( callback );
                                } else {
                                        /*jshint evil:true */
                                        document.write( mw.html.element( 'script', { 'src': src }, '' ) );
                                        if ( callback ) {
                                                // Document.write is synchronous, so this is called when it's done.
                                                // FIXME: That's a lie. doc.write isn't actually synchronous.
                                                callback();
                                        }
                                }
                        }

                        /**
                         * Executes a loaded module, making it ready to use
                         *
                         * @private
                         * @param {string} module Module name to execute
                         */
                        function execute( module ) {
                                var key, value, media, i, urls, cssHandle, checkCssHandles,
                                        cssHandlesRegistered = false;

                                if ( !hasOwn.call( registry, module ) ) {
                                        throw new Error( 'Module has not been registered yet: ' + module );
                                } else if ( registry[module].state === 'registered' ) {
                                        throw new Error( 'Module has not been requested from the server yet: ' + module );
                                } else if ( registry[module].state === 'loading' ) {
                                        throw new Error( 'Module has not completed loading yet: ' + module );
                                } else if ( registry[module].state === 'ready' ) {
                                        throw new Error( 'Module has already been executed: ' + module );
                                }

                                /**
                                 * Define loop-function here for efficiency
                                 * and to avoid re-using badly scoped variables.
                                 * @ignore
                                 */
                                function addLink( media, url ) {
                                        var el = document.createElement( 'link' );
                                        // Support: IE
                                        // Insert in document *before* setting href
                                        getMarker().before( el );
                                        el.rel = 'stylesheet';
                                        if ( media && media !== 'all' ) {
                                                el.media = media;
                                        }
                                        // If you end up here from an IE exception "SCRIPT: Invalid property value.",
                                        // see #addEmbeddedCSS, bug 31676, and bug 47277 for details.
                                        el.href = url;
                                }

                                function runScript() {
                                        var script, markModuleReady, nestedAddScript;
                                        try {
                                                script = registry[module].script;
                                                markModuleReady = function () {
                                                        registry[module].state = 'ready';
                                                        handlePending( module );
                                                };
                                                nestedAddScript = function ( arr, callback, async, i ) {
                                                        // Recursively call addScript() in its own callback
                                                        // for each element of arr.
                                                        if ( i >= arr.length ) {
                                                                // We're at the end of the array
                                                                callback();
                                                                return;
                                                        }

                                                        addScript( arr[i], function () {
                                                                nestedAddScript( arr, callback, async, i + 1 );
                                                        }, async );
                                                };

                                                if ( $.isArray( script ) ) {
                                                        nestedAddScript( script, markModuleReady, registry[module].async, 0 );
                                                } else if ( $.isFunction( script ) ) {
                                                        registry[module].state = 'ready';
                                                        // Pass jQuery twice so that the signature of the closure which wraps
                                                        // the script can bind both '$' and 'jQuery'.
                                                        script( $, $ );
                                                        handlePending( module );
                                                }
                                        } catch ( e ) {
                                                // This needs to NOT use mw.log because these errors are common in production mode
                                                // and not in debug mode, such as when a symbol that should be global isn't exported
                                                log( 'Exception thrown by ' + module, e );
                                                registry[module].state = 'error';
                                                handlePending( module );
                                        }
                                }

                                // This used to be inside runScript, but since that is now fired asychronously
                                // (after CSS is loaded) we need to set it here right away. It is crucial that
                                // when execute() is called this is set synchronously, otherwise modules will get
                                // executed multiple times as the registry will state that it isn't loading yet.
                                registry[module].state = 'loading';

                                // Add localizations to message system
                                if ( $.isPlainObject( registry[module].messages ) ) {
                                        mw.messages.set( registry[module].messages );
                                }

                                // Initialise templates
                                if ( registry[module].templates ) {
                                        mw.templates.set( module, registry[module].templates );
                                }

                                if ( $.isReady || registry[module].async ) {
                                        // Make sure we don't run the scripts until all (potentially asynchronous)
                                        // stylesheet insertions have completed.
                                        ( function () {
                                                var pending = 0;
                                                checkCssHandles = function () {
                                                        // cssHandlesRegistered ensures we don't take off too soon, e.g. when
                                                        // one of the cssHandles is fired while we're still creating more handles.
                                                        if ( cssHandlesRegistered && pending === 0 && runScript ) {
                                                                runScript();
                                                                runScript = undefined; // Revoke
                                                        }
                                                };
                                                cssHandle = function () {
                                                        var check = checkCssHandles;
                                                        pending++;
                                                        return function () {
                                                                if ( check ) {
                                                                        pending--;
                                                                        check();
                                                                        check = undefined; // Revoke
                                                                }
                                                        };
                                                };
                                        }() );
                                } else {
                                        // We are in blocking mode, and so we can't afford to wait for CSS
                                        cssHandle = function () {};
                                        // Run immediately
                                        checkCssHandles = runScript;
                                }

                                // Process styles (see also mw.loader.implement)
                                // * back-compat: { <media>: css }
                                // * back-compat: { <media>: [url, ..] }
                                // * { "css": [css, ..] }
                                // * { "url": { <media>: [url, ..] } }
                                if ( $.isPlainObject( registry[module].style ) ) {
                                        for ( key in registry[module].style ) {
                                                value = registry[module].style[key];
                                                media = undefined;

                                                if ( key !== 'url' && key !== 'css' ) {
                                                        // Backwards compatibility, key is a media-type
                                                        if ( typeof value === 'string' ) {
                                                                // back-compat: { <media>: css }
                                                                // Ignore 'media' because it isn't supported (nor was it used).
                                                                // Strings are pre-wrapped in "@media". The media-type was just ""
                                                                // (because it had to be set to something).
                                                                // This is one of the reasons why this format is no longer used.
                                                                addEmbeddedCSS( value, cssHandle() );
                                                        } else {
                                                                // back-compat: { <media>: [url, ..] }
                                                                media = key;
                                                                key = 'bc-url';
                                                        }
                                                }

                                                // Array of css strings in key 'css',
                                                // or back-compat array of urls from media-type
                                                if ( $.isArray( value ) ) {
                                                        for ( i = 0; i < value.length; i += 1 ) {
                                                                if ( key === 'bc-url' ) {
                                                                        // back-compat: { <media>: [url, ..] }
                                                                        addLink( media, value[i] );
                                                                } else if ( key === 'css' ) {
                                                                        // { "css": [css, ..] }
                                                                        addEmbeddedCSS( value[i], cssHandle() );
                                                                }
                                                        }
                                                // Not an array, but a regular object
                                                // Array of urls inside media-type key
                                                } else if ( typeof value === 'object' ) {
                                                        // { "url": { <media>: [url, ..] } }
                                                        for ( media in value ) {
                                                                urls = value[media];
                                                                for ( i = 0; i < urls.length; i += 1 ) {
                                                                        addLink( media, urls[i] );
                                                                }
                                                        }
                                                }
                                        }
                                }

                                // Kick off.
                                cssHandlesRegistered = true;
                                checkCssHandles();
                        }

                        /**
                         * Adds a dependencies to the queue with optional callbacks to be run
                         * when the dependencies are ready or fail
                         *
                         * @private
                         * @param {string|string[]} dependencies Module name or array of string module names
                         * @param {Function} [ready] Callback to execute when all dependencies are ready
                         * @param {Function} [error] Callback to execute when any dependency fails
                         * @param {boolean} [async=false] Whether to load modules asynchronously.
                         *  Ignored (and defaulted to `true`) if the document-ready event has already occurred.
                         */
                        function request( dependencies, ready, error, async ) {
                                var n;

                                // Allow calling by single module name
                                if ( typeof dependencies === 'string' ) {
                                        dependencies = [dependencies];
                                }

                                // Add ready and error callbacks if they were given
                                if ( ready !== undefined || error !== undefined ) {
                                        jobs[jobs.length] = {
                                                'dependencies': filter(
                                                        ['registered', 'loading', 'loaded'],
                                                        dependencies
                                                ),
                                                'ready': ready,
                                                'error': error
                                        };
                                }

                                // Queue up any dependencies that are registered
                                dependencies = filter( ['registered'], dependencies );
                                for ( n = 0; n < dependencies.length; n += 1 ) {
                                        if ( $.inArray( dependencies[n], queue ) === -1 ) {
                                                queue[queue.length] = dependencies[n];
                                                if ( async ) {
                                                        // Mark this module as async in the registry
                                                        registry[dependencies[n]].async = true;
                                                }
                                        }
                                }

                                // Work the queue
                                mw.loader.work();
                        }

                        function sortQuery( o ) {
                                var sorted = {}, key, a = [];
                                for ( key in o ) {
                                        if ( hasOwn.call( o, key ) ) {
                                                a.push( key );
                                        }
                                }
                                a.sort();
                                for ( key = 0; key < a.length; key += 1 ) {
                                        sorted[a[key]] = o[a[key]];
                                }
                                return sorted;
                        }

                        /**
                         * Converts a module map of the form { foo: [ 'bar', 'baz' ], bar: [ 'baz, 'quux' ] }
                         * to a query string of the form foo.bar,baz|bar.baz,quux
                         * @private
                         */
                        function buildModulesString( moduleMap ) {
                                var arr = [], p, prefix;
                                for ( prefix in moduleMap ) {
                                        p = prefix === '' ? '' : prefix + '.';
                                        arr.push( p + moduleMap[prefix].join( ',' ) );
                                }
                                return arr.join( '|' );
                        }

                        /**
                         * Asynchronously append a script tag to the end of the body
                         * that invokes load.php
                         * @private
                         * @param {Object} moduleMap Module map, see #buildModulesString
                         * @param {Object} currReqBase Object with other parameters (other than 'modules') to use in the request
                         * @param {string} sourceLoadScript URL of load.php
                         * @param {boolean} async Whether to load modules asynchronously.
                         *  Ignored (and defaulted to `true`) if the document-ready event has already occurred.
                         */
                        function doRequest( moduleMap, currReqBase, sourceLoadScript, async ) {
                                var request = $.extend(
                                        { modules: buildModulesString( moduleMap ) },
                                        currReqBase
                                );
                                request = sortQuery( request );
                                // Support: IE6
                                // Append &* to satisfy load.php's WebRequest::checkUrlExtension test. This script
                                // isn't actually used in IE6, but MediaWiki enforces it in general.
                                addScript( sourceLoadScript + '?' + $.param( request ) + '&*', null, async );
                        }

                        /**
                         * Resolve indexed dependencies.
                         *
                         * ResourceLoader uses an optimization to save space which replaces module names in
                         * dependency lists with the index of that module within the array of module
                         * registration data if it exists. The benefit is a significant reduction in the data
                         * size of the startup module. This function changes those dependency lists back to
                         * arrays of strings.
                         *
                         * @param {Array} modules Modules array
                         */
                        function resolveIndexedDependencies( modules ) {
                                var i, iLen, j, jLen, module, dependency;

                                // Expand indexed dependency names
                                for ( i = 0, iLen = modules.length; i < iLen; i++ ) {
                                        module = modules[i];
                                        if ( module[2] ) {
                                                for ( j = 0, jLen = module[2].length; j < jLen; j++ ) {
                                                        dependency = module[2][j];
                                                        if ( typeof dependency === 'number' ) {
                                                                module[2][j] = modules[dependency][0];
                                                        }
                                                }
                                        }
                                }
                        }

                        /* Public Members */
                        return {
                                /**
                                 * The module registry is exposed as an aid for debugging and inspecting page
                                 * state; it is not a public interface for modifying the registry.
                                 *
                                 * @see #registry
                                 * @property
                                 * @private
                                 */
                                moduleRegistry: registry,

                                /**
                                 * @inheritdoc #newStyleTag
                                 * @method
                                 */
                                addStyleTag: newStyleTag,

                                /**
                                 * Batch-request queued dependencies from the server.
                                 */
                                work: function () {
                                        var     reqBase, splits, maxQueryLength, q, b, bSource, bGroup, bSourceGroup,
                                                source, concatSource, origBatch, group, g, i, modules, maxVersion, sourceLoadScript,
                                                currReqBase, currReqBaseLength, moduleMap, l,
                                                lastDotIndex, prefix, suffix, bytesAdded, async;

                                        // Build a list of request parameters common to all requests.
                                        reqBase = {
                                                skin: mw.config.get( 'skin' ),
                                                lang: mw.config.get( 'wgUserLanguage' ),
                                                debug: mw.config.get( 'debug' )
                                        };
                                        // Split module batch by source and by group.
                                        splits = {};
                                        maxQueryLength = mw.config.get( 'wgResourceLoaderMaxQueryLength', -1 );

                                        // Appends a list of modules from the queue to the batch
                                        for ( q = 0; q < queue.length; q += 1 ) {
                                                // Only request modules which are registered
                                                if ( hasOwn.call( registry, queue[q] ) && registry[queue[q]].state === 'registered' ) {
                                                        // Prevent duplicate entries
                                                        if ( $.inArray( queue[q], batch ) === -1 ) {
                                                                batch[batch.length] = queue[q];
                                                                // Mark registered modules as loading
                                                                registry[queue[q]].state = 'loading';
                                                        }
                                                }
                                        }

                                        mw.loader.store.init();
                                        if ( mw.loader.store.enabled ) {
                                                concatSource = [];
                                                origBatch = batch;
                                                batch = $.grep( batch, function ( module ) {
                                                        var source = mw.loader.store.get( module );
                                                        if ( source ) {
                                                                concatSource.push( source );
                                                                return false;
                                                        }
                                                        return true;
                                                } );
                                                try {
                                                        $.globalEval( concatSource.join( ';' ) );
                                                } catch ( err ) {
                                                        // Not good, the cached mw.loader.implement calls failed! This should
                                                        // never happen, barring ResourceLoader bugs, browser bugs and PEBKACs.
                                                        // Depending on how corrupt the string is, it is likely that some
                                                        // modules' implement() succeeded while the ones after the error will
                                                        // never run and leave their modules in the 'loading' state forever.

                                                        // Since this is an error not caused by an individual module but by
                                                        // something that infected the implement call itself, don't take any
                                                        // risks and clear everything in this cache.
                                                        mw.loader.store.clear();
                                                        // Re-add the ones still pending back to the batch and let the server
                                                        // repopulate these modules to the cache.
                                                        // This means that at most one module will be useless (the one that had
                                                        // the error) instead of all of them.
                                                        log( 'Error while evaluating data from mw.loader.store', err );
                                                        origBatch = $.grep( origBatch, function ( module ) {
                                                                return registry[module].state === 'loading';
                                                        } );
                                                        batch = batch.concat( origBatch );
                                                }
                                        }

                                        // Early exit if there's nothing to load...
                                        if ( !batch.length ) {
                                                return;
                                        }

                                        // The queue has been processed into the batch, clear up the queue.
                                        queue = [];

                                        // Always order modules alphabetically to help reduce cache
                                        // misses for otherwise identical content.
                                        batch.sort();

                                        // Split batch by source and by group.
                                        for ( b = 0; b < batch.length; b += 1 ) {
                                                bSource = registry[batch[b]].source;
                                                bGroup = registry[batch[b]].group;
                                                if ( !hasOwn.call( splits, bSource ) ) {
                                                        splits[bSource] = {};
                                                }
                                                if ( !hasOwn.call( splits[bSource], bGroup ) ) {
                                                        splits[bSource][bGroup] = [];
                                                }
                                                bSourceGroup = splits[bSource][bGroup];
                                                bSourceGroup[bSourceGroup.length] = batch[b];
                                        }

                                        // Clear the batch - this MUST happen before we append any
                                        // script elements to the body or it's possible that a script
                                        // will be locally cached, instantly load, and work the batch
                                        // again, all before we've cleared it causing each request to
                                        // include modules which are already loaded.
                                        batch = [];

                                        for ( source in splits ) {

                                                sourceLoadScript = sources[source];

                                                for ( group in splits[source] ) {

                                                        // Cache access to currently selected list of
                                                        // modules for this group from this source.
                                                        modules = splits[source][group];

                                                        // Calculate the highest timestamp
                                                        maxVersion = 0;
                                                        for ( g = 0; g < modules.length; g += 1 ) {
                                                                if ( registry[modules[g]].version > maxVersion ) {
                                                                        maxVersion = registry[modules[g]].version;
                                                                }
                                                        }

                                                        currReqBase = $.extend( { version: formatVersionNumber( maxVersion ) }, reqBase );
                                                        // For user modules append a user name to the request.
                                                        if ( group === 'user' && mw.config.get( 'wgUserName' ) !== null ) {
                                                                currReqBase.user = mw.config.get( 'wgUserName' );
                                                        }
                                                        currReqBaseLength = $.param( currReqBase ).length;
                                                        async = true;
                                                        // We may need to split up the request to honor the query string length limit,
                                                        // so build it piece by piece.
                                                        l = currReqBaseLength + 9; // '&modules='.length == 9

                                                        moduleMap = {}; // { prefix: [ suffixes ] }

                                                        for ( i = 0; i < modules.length; i += 1 ) {
                                                                // Determine how many bytes this module would add to the query string
                                                                lastDotIndex = modules[i].lastIndexOf( '.' );

                                                                // If lastDotIndex is -1, substr() returns an empty string
                                                                prefix = modules[i].substr( 0, lastDotIndex );
                                                                suffix = modules[i].slice( lastDotIndex + 1 );

                                                                bytesAdded = hasOwn.call( moduleMap, prefix )
                                                                        ? suffix.length + 3 // '%2C'.length == 3
                                                                        : modules[i].length + 3; // '%7C'.length == 3

                                                                // If the request would become too long, create a new one,
                                                                // but don't create empty requests
                                                                if ( maxQueryLength > 0 && !$.isEmptyObject( moduleMap ) && l + bytesAdded > maxQueryLength ) {
                                                                        // This request would become too long, create a new one
                                                                        // and fire off the old one
                                                                        doRequest( moduleMap, currReqBase, sourceLoadScript, async );
                                                                        moduleMap = {};
                                                                        async = true;
                                                                        l = currReqBaseLength + 9;
                                                                }
                                                                if ( !hasOwn.call( moduleMap, prefix ) ) {
                                                                        moduleMap[prefix] = [];
                                                                }
                                                                moduleMap[prefix].push( suffix );
                                                                if ( !registry[modules[i]].async ) {
                                                                        // If this module is blocking, make the entire request blocking
                                                                        // This is slightly suboptimal, but in practice mixing of blocking
                                                                        // and async modules will only occur in debug mode.
                                                                        async = false;
                                                                }
                                                                l += bytesAdded;
                                                        }
                                                        // If there's anything left in moduleMap, request that too
                                                        if ( !$.isEmptyObject( moduleMap ) ) {
                                                                doRequest( moduleMap, currReqBase, sourceLoadScript, async );
                                                        }
                                                }
                                        }
                                },

                                /**
                                 * Register a source.
                                 *
                                 * The #work method will use this information to split up requests by source.
                                 *
                                 *     mw.loader.addSource( 'mediawikiwiki', '//www.mediawiki.org/w/load.php' );
                                 *
                                 * @param {string} id Short string representing a source wiki, used internally for
                                 *  registered modules to indicate where they should be loaded from (usually lowercase a-z).
                                 * @param {Object|string} loadUrl load.php url, may be an object for backwards-compatibility
                                 * @return {boolean}
                                 */
                                addSource: function ( id, loadUrl ) {
                                        var source;
                                        // Allow multiple additions
                                        if ( typeof id === 'object' ) {
                                                for ( source in id ) {
                                                        mw.loader.addSource( source, id[source] );
                                                }
                                                return true;
                                        }

                                        if ( hasOwn.call( sources, id ) ) {
                                                throw new Error( 'source already registered: ' + id );
                                        }

                                        if ( typeof loadUrl === 'object' ) {
                                                loadUrl = loadUrl.loadScript;
                                        }

                                        sources[id] = loadUrl;

                                        return true;
                                },

                                /**
                                 * Register a module, letting the system know about it and its
                                 * properties. Startup modules contain calls to this function.
                                 *
                                 * When using multiple module registration by passing an array, dependencies that
                                 * are specified as references to modules within the array will be resolved before
                                 * the modules are registered.
                                 *
                                 * @param {string|Array} module Module name or array of arrays, each containing
                                 *  a list of arguments compatible with this method
                                 * @param {number} version Module version number as a timestamp (falls backs to 0)
                                 * @param {string|Array|Function} dependencies One string or array of strings of module
                                 *  names on which this module depends, or a function that returns that array.
                                 * @param {string} [group=null] Group which the module is in
                                 * @param {string} [source='local'] Name of the source
                                 * @param {string} [skip=null] Script body of the skip function
                                 */
                                register: function ( module, version, dependencies, group, source, skip ) {
                                        var i, len;
                                        // Allow multiple registration
                                        if ( typeof module === 'object' ) {
                                                resolveIndexedDependencies( module );
                                                for ( i = 0, len = module.length; i < len; i++ ) {
                                                        // module is an array of module names
                                                        if ( typeof module[i] === 'string' ) {
                                                                mw.loader.register( module[i] );
                                                        // module is an array of arrays
                                                        } else if ( typeof module[i] === 'object' ) {
                                                                mw.loader.register.apply( mw.loader, module[i] );
                                                        }
                                                }
                                                return;
                                        }
                                        // Validate input
                                        if ( typeof module !== 'string' ) {
                                                throw new Error( 'module must be a string, not a ' + typeof module );
                                        }
                                        if ( hasOwn.call( registry, module ) ) {
                                                throw new Error( 'module already registered: ' + module );
                                        }
                                        // List the module as registered
                                        registry[module] = {
                                                version: version !== undefined ? parseInt( version, 10 ) : 0,
                                                dependencies: [],
                                                group: typeof group === 'string' ? group : null,
                                                source: typeof source === 'string' ? source : 'local',
                                                state: 'registered',
                                                skip: typeof skip === 'string' ? skip : null
                                        };
                                        if ( typeof dependencies === 'string' ) {
                                                // Allow dependencies to be given as a single module name
                                                registry[module].dependencies = [ dependencies ];
                                        } else if ( typeof dependencies === 'object' || $.isFunction( dependencies ) ) {
                                                // Allow dependencies to be given as an array of module names
                                                // or a function which returns an array
                                                registry[module].dependencies = dependencies;
                                        }
                                },

                                /**
                                 * Implement a module given the components that make up the module.
                                 *
                                 * When #load or #using requests one or more modules, the server
                                 * response contain calls to this function.
                                 *
                                 * All arguments are required.
                                 *
                                 * @param {string} module Name of module
                                 * @param {Function|Array} script Function with module code or Array of URLs to
                                 *  be used as the src attribute of a new `<script>` tag.
                                 * @param {Object} [style] Should follow one of the following patterns:
                                 *
                                 *     { "css": [css, ..] }
                                 *     { "url": { <media>: [url, ..] } }
                                 *
                                 * And for backwards compatibility (needs to be supported forever due to caching):
                                 *
                                 *     { <media>: css }
                                 *     { <media>: [url, ..] }
                                 *
                                 * The reason css strings are not concatenated anymore is bug 31676. We now check
                                 * whether it's safe to extend the stylesheet (see #canExpandStylesheetWith).
                                 *
                                 * @param {Object} [msgs] List of key/value pairs to be added to mw#messages.
                                 * @param {Object} [templates] List of key/value pairs to be added to mw#templates.
                                 */
                                implement: function ( module, script, style, msgs, templates ) {
                                        // Validate input
                                        if ( typeof module !== 'string' ) {
                                                throw new Error( 'module must be of type string, not ' + typeof module );
                                        }
                                        if ( script && !$.isFunction( script ) && !$.isArray( script ) ) {
                                                throw new Error( 'script must be of type function or array, not ' + typeof script );
                                        }
                                        if ( style && !$.isPlainObject( style ) ) {
                                                throw new Error( 'style must be of type object, not ' + typeof style );
                                        }
                                        if ( msgs && !$.isPlainObject( msgs ) ) {
                                                throw new Error( 'msgs must be of type object, not a ' + typeof msgs );
                                        }
                                        if ( templates && !$.isPlainObject( templates ) ) {
                                                throw new Error( 'templates must be of type object, not a ' + typeof templates );
                                        }
                                        // Automatically register module
                                        if ( !hasOwn.call( registry, module ) ) {
                                                mw.loader.register( module );
                                        }
                                        // Check for duplicate implementation
                                        if ( hasOwn.call( registry, module ) && registry[module].script !== undefined ) {
                                                throw new Error( 'module already implemented: ' + module );
                                        }
                                        // Attach components
                                        registry[module].script = script || [];
                                        registry[module].style = style || {};
                                        registry[module].messages = msgs || {};
                                        registry[module].templates = templates || {};
                                        // The module may already have been marked as erroneous
                                        if ( $.inArray( registry[module].state, ['error', 'missing'] ) === -1 ) {
                                                registry[module].state = 'loaded';
                                                if ( allReady( registry[module].dependencies ) ) {
                                                        execute( module );
                                                }
                                        }
                                },

                                /**
                                 * Execute a function as soon as one or more required modules are ready.
                                 *
                                 * Example of inline dependency on OOjs:
                                 *
                                 *     mw.loader.using( 'oojs', function () {
                                 *         OO.compare( [ 1 ], [ 1 ] );
                                 *     } );
                                 *
                                 * @param {string|Array} dependencies Module name or array of modules names the callback
                                 *  dependends on to be ready before executing
                                 * @param {Function} [ready] Callback to execute when all dependencies are ready
                                 * @param {Function} [error] Callback to execute if one or more dependencies failed
                                 * @return {jQuery.Promise}
                                 * @since 1.23 this returns a promise
                                 */
                                using: function ( dependencies, ready, error ) {
                                        var deferred = $.Deferred();

                                        // Allow calling with a single dependency as a string
                                        if ( typeof dependencies === 'string' ) {
                                                dependencies = [ dependencies ];
                                        } else if ( !$.isArray( dependencies ) ) {
                                                // Invalid input
                                                throw new Error( 'Dependencies must be a string or an array' );
                                        }

                                        if ( ready ) {
                                                deferred.done( ready );
                                        }
                                        if ( error ) {
                                                deferred.fail( error );
                                        }

                                        // Resolve entire dependency map
                                        dependencies = resolve( dependencies );
                                        if ( allReady( dependencies ) ) {
                                                // Run ready immediately
                                                deferred.resolve();
                                        } else if ( filter( ['error', 'missing'], dependencies ).length ) {
                                                // Execute error immediately if any dependencies have errors
                                                deferred.reject(
                                                        new Error( 'One or more dependencies failed to load' ),
                                                        dependencies
                                                );
                                        } else {
                                                // Not all dependencies are ready: queue up a request
                                                request( dependencies, deferred.resolve, deferred.reject );
                                        }

                                        return deferred.promise();
                                },

                                /**
                                 * Load an external script or one or more modules.
                                 *
                                 * @param {string|Array} modules Either the name of a module, array of modules,
                                 *  or a URL of an external script or style
                                 * @param {string} [type='text/javascript'] MIME type to use if calling with a URL of an
                                 *  external script or style; acceptable values are "text/css" and
                                 *  "text/javascript"; if no type is provided, text/javascript is assumed.
                                 * @param {boolean} [async] Whether to load modules asynchronously.
                                 *  Ignored (and defaulted to `true`) if the document-ready event has already occurred.
                                 *  Defaults to `true` if loading a URL, `false` otherwise.
                                 */
                                load: function ( modules, type, async ) {
                                        var filtered, m, module, l;

                                        // Validate input
                                        if ( typeof modules !== 'object' && typeof modules !== 'string' ) {
                                                throw new Error( 'modules must be a string or an array, not a ' + typeof modules );
                                        }
                                        // Allow calling with an external url or single dependency as a string
                                        if ( typeof modules === 'string' ) {
                                                if ( /^(https?:)?\/\//.test( modules ) ) {
                                                        if ( async === undefined ) {
                                                                // Assume async for bug 34542
                                                                async = true;
                                                        }
                                                        if ( type === 'text/css' ) {
                                                                // Support: IE 7-8
                                                                // Use properties instead of attributes as IE throws security
                                                                // warnings when inserting a <link> tag with a protocol-relative
                                                                // URL set though attributes - when on HTTPS. See bug 41331.
                                                                l = document.createElement( 'link' );
                                                                l.rel = 'stylesheet';
                                                                l.href = modules;
                                                                $( 'head' ).append( l );
                                                                return;
                                                        }
                                                        if ( type === 'text/javascript' || type === undefined ) {
                                                                addScript( modules, null, async );
                                                                return;
                                                        }
                                                        // Unknown type
                                                        throw new Error( 'invalid type for external url, must be text/css or text/javascript. not ' + type );
                                                }
                                                // Called with single module
                                                modules = [ modules ];
                                        }

                                        // Filter out undefined modules, otherwise resolve() will throw
                                        // an exception for trying to load an undefined module.
                                        // Undefined modules are acceptable here in load(), because load() takes
                                        // an array of unrelated modules, whereas the modules passed to
                                        // using() are related and must all be loaded.
                                        for ( filtered = [], m = 0; m < modules.length; m += 1 ) {
                                                if ( hasOwn.call( registry, modules[m] ) ) {
                                                        module = registry[modules[m]];
                                                        if ( $.inArray( module.state, ['error', 'missing'] ) === -1 ) {
                                                                filtered[filtered.length] = modules[m];
                                                        }
                                                }
                                        }

                                        if ( filtered.length === 0 ) {
                                                return;
                                        }
                                        // Resolve entire dependency map
                                        filtered = resolve( filtered );
                                        // If all modules are ready, nothing to be done
                                        if ( allReady( filtered ) ) {
                                                return;
                                        }
                                        // If any modules have errors: also quit.
                                        if ( filter( ['error', 'missing'], filtered ).length ) {
                                                return;
                                        }
                                        // Since some modules are not yet ready, queue up a request.
                                        request( filtered, undefined, undefined, async );
                                },

                                /**
                                 * Change the state of one or more modules.
                                 *
                                 * @param {string|Object} module Module name or object of module name/state pairs
                                 * @param {string} state State name
                                 */
                                state: function ( module, state ) {
                                        var m;

                                        if ( typeof module === 'object' ) {
                                                for ( m in module ) {
                                                        mw.loader.state( m, module[m] );
                                                }
                                                return;
                                        }
                                        if ( !hasOwn.call( registry, module ) ) {
                                                mw.loader.register( module );
                                        }
                                        if ( $.inArray( state, ['ready', 'error', 'missing'] ) !== -1
                                                && registry[module].state !== state ) {
                                                // Make sure pending modules depending on this one get executed if their
                                                // dependencies are now fulfilled!
                                                registry[module].state = state;
                                                handlePending( module );
                                        } else {
                                                registry[module].state = state;
                                        }
                                },

                                /**
                                 * Get the version of a module.
                                 *
                                 * @param {string} module Name of module
                                 * @return {string|null} The version, or null if the module (or its version) is not
                                 *  in the registry.
                                 */
                                getVersion: function ( module ) {
                                        if ( !hasOwn.call( registry, module ) || registry[module].version === undefined ) {
                                                return null;
                                        }
                                        return formatVersionNumber( registry[module].version );
                                },

                                /**
                                 * Get the state of a module.
                                 *
                                 * @param {string} module Name of module
                                 * @return {string|null} The state, or null if the module (or its state) is not
                                 *  in the registry.
                                 */
                                getState: function ( module ) {
                                        if ( !hasOwn.call( registry, module ) || registry[module].state === undefined ) {
                                                return null;
                                        }
                                        return registry[module].state;
                                },

                                /**
                                 * Get the names of all registered modules.
                                 *
                                 * @return {Array}
                                 */
                                getModuleNames: function () {
                                        return $.map( registry, function ( i, key ) {
                                                return key;
                                        } );
                                },

                                /**
                                 * @inheritdoc mw.inspect#runReports
                                 * @method
                                 */
                                inspect: function () {
                                        var args = slice.call( arguments );
                                        mw.loader.using( 'mediawiki.inspect', function () {
                                                mw.inspect.runReports.apply( mw.inspect, args );
                                        } );
                                },

                                /**
                                 * On browsers that implement the localStorage API, the module store serves as a
                                 * smart complement to the browser cache. Unlike the browser cache, the module store
                                 * can slice a concatenated response from ResourceLoader into its constituent
                                 * modules and cache each of them separately, using each module's versioning scheme
                                 * to determine when the cache should be invalidated.
                                 *
                                 * @singleton
                                 * @class mw.loader.store
                                 */
                                store: {
                                        // Whether the store is in use on this page.
                                        enabled: null,

                                        // The contents of the store, mapping '[module name]@[version]' keys
                                        // to module implementations.
                                        items: {},

                                        // Cache hit stats
                                        stats: { hits: 0, misses: 0, expired: 0 },

                                        /**
                                         * Construct a JSON-serializable object representing the content of the store.
                                         * @return {Object} Module store contents.
                                         */
                                        toJSON: function () {
                                                return { items: mw.loader.store.items, vary: mw.loader.store.getVary() };
                                        },

                                        /**
                                         * Get the localStorage key for the entire module store. The key references
                                         * $wgDBname to prevent clashes between wikis which share a common host.
                                         *
                                         * @return {string} localStorage item key
                                         */
                                        getStoreKey: function () {
                                                return 'MediaWikiModuleStore:' + mw.config.get( 'wgDBname' );
                                        },

                                        /**
                                         * Get a key on which to vary the module cache.
                                         * @return {string} String of concatenated vary conditions.
                                         */
                                        getVary: function () {
                                                return [
                                                        mw.config.get( 'skin' ),
                                                        mw.config.get( 'wgResourceLoaderStorageVersion' ),
                                                        mw.config.get( 'wgUserLanguage' )
                                                ].join( ':' );
                                        },

                                        /**
                                         * Get a key for a specific module. The key format is '[name]@[version]'.
                                         *
                                         * @param {string} module Module name
                                         * @return {string|null} Module key or null if module does not exist
                                         */
                                        getModuleKey: function ( module ) {
                                                return hasOwn.call( registry, module ) ?
                                                        ( module + '@' + registry[module].version ) : null;
                                        },

                                        /**
                                         * Initialize the store.
                                         *
                                         * Retrieves store from localStorage and (if successfully retrieved) decoding
                                         * the stored JSON value to a plain object.
                                         *
                                         * The try / catch block is used for JSON & localStorage feature detection.
                                         * See the in-line documentation for Modernizr's localStorage feature detection
                                         * code for a full account of why we need a try / catch:
                                         * <https://github.com/Modernizr/Modernizr/blob/v2.7.1/modernizr.js#L771-L796>.
                                         */
                                        init: function () {
                                                var raw, data;

                                                if ( mw.loader.store.enabled !== null ) {
                                                        // Init already ran
                                                        return;
                                                }

                                                if ( !mw.config.get( 'wgResourceLoaderStorageEnabled' ) ) {
                                                        // Disabled by configuration.
                                                        // Clear any previous store to free up space. (T66721)
                                                        mw.loader.store.clear();
                                                        mw.loader.store.enabled = false;
                                                        return;
                                                }
                                                if ( mw.config.get( 'debug' ) ) {
                                                        // Disable module store in debug mode
                                                        mw.loader.store.enabled = false;
                                                        return;
                                                }

                                                try {
                                                        raw = localStorage.getItem( mw.loader.store.getStoreKey() );
                                                        // If we get here, localStorage is available; mark enabled
                                                        mw.loader.store.enabled = true;
                                                        data = JSON.parse( raw );
                                                        if ( data && typeof data.items === 'object' && data.vary === mw.loader.store.getVary() ) {
                                                                mw.loader.store.items = data.items;
                                                                return;
                                                        }
                                                } catch ( e ) {
                                                        log( 'Storage error', e );
                                                }

                                                if ( raw === undefined ) {
                                                        // localStorage failed; disable store
                                                        mw.loader.store.enabled = false;
                                                } else {
                                                        mw.loader.store.update();
                                                }
                                        },

                                        /**
                                         * Retrieve a module from the store and update cache hit stats.
                                         *
                                         * @param {string} module Module name
                                         * @return {string|boolean} Module implementation or false if unavailable
                                         */
                                        get: function ( module ) {
                                                var key;

                                                if ( !mw.loader.store.enabled ) {
                                                        return false;
                                                }

                                                key = mw.loader.store.getModuleKey( module );
                                                if ( key in mw.loader.store.items ) {
                                                        mw.loader.store.stats.hits++;
                                                        return mw.loader.store.items[key];
                                                }
                                                mw.loader.store.stats.misses++;
                                                return false;
                                        },

                                        /**
                                         * Stringify a module and queue it for storage.
                                         *
                                         * @param {string} module Module name
                                         * @param {Object} descriptor The module's descriptor as set in the registry
                                         */
                                        set: function ( module, descriptor ) {
                                                var args, key;

                                                if ( !mw.loader.store.enabled ) {
                                                        return false;
                                                }

                                                key = mw.loader.store.getModuleKey( module );

                                                if (
                                                        // Already stored a copy of this exact version
                                                        key in mw.loader.store.items ||
                                                        // Module failed to load
                                                        descriptor.state !== 'ready' ||
                                                        // Unversioned, private, or site-/user-specific
                                                        ( !descriptor.version || $.inArray( descriptor.group, [ 'private', 'user', 'site' ] ) !== -1 ) ||
                                                        // Partial descriptor
                                                        $.inArray( undefined, [ descriptor.script, descriptor.style,
                                                                        descriptor.messages, descriptor.templates ] ) !== -1
                                                ) {
                                                        // Decline to store
                                                        return false;
                                                }

                                                try {
                                                        args = [
                                                                JSON.stringify( module ),
                                                                typeof descriptor.script === 'function' ?
                                                                        String( descriptor.script ) :
                                                                        JSON.stringify( descriptor.script ),
                                                                JSON.stringify( descriptor.style ),
                                                                JSON.stringify( descriptor.messages ),
                                                                JSON.stringify( descriptor.templates )
                                                        ];
                                                        // Attempted workaround for a possible Opera bug (bug 57567).
                                                        // This regex should never match under sane conditions.
                                                        if ( /^\s*\(/.test( args[1] ) ) {
                                                                args[1] = 'function' + args[1];
                                                                log( 'Detected malformed function stringification (bug 57567)' );
                                                        }
                                                } catch ( e ) {
                                                        log( 'Storage error', e );
                                                        return;
                                                }

                                                mw.loader.store.items[key] = 'mw.loader.implement(' + args.join( ',' ) + ');';
                                                mw.loader.store.update();
                                        },

                                        /**
                                         * Iterate through the module store, removing any item that does not correspond
                                         * (in name and version) to an item in the module registry.
                                         */
                                        prune: function () {
                                                var key, module;

                                                if ( !mw.loader.store.enabled ) {
                                                        return false;
                                                }

                                                for ( key in mw.loader.store.items ) {
                                                        module = key.slice( 0, key.indexOf( '@' ) );
                                                        if ( mw.loader.store.getModuleKey( module ) !== key ) {
                                                                mw.loader.store.stats.expired++;
                                                                delete mw.loader.store.items[key];
                                                        }
                                                }
                                        },

                                        /**
                                         * Clear the entire module store right now.
                                         */
                                        clear: function () {
                                                mw.loader.store.items = {};
                                                localStorage.removeItem( mw.loader.store.getStoreKey() );
                                        },

                                        /**
                                         * Sync modules to localStorage.
                                         *
                                         * This function debounces localStorage updates. When called multiple times in
                                         * quick succession, the calls are coalesced into a single update operation.
                                         * This allows us to call #update without having to consider the module load
                                         * queue; the call to localStorage.setItem will be naturally deferred until the
                                         * page is quiescent.
                                         *
                                         * Because localStorage is shared by all pages with the same origin, if multiple
                                         * pages are loaded with different module sets, the possibility exists that
                                         * modules saved by one page will be clobbered by another. But the impact would
                                         * be minor and the problem would be corrected by subsequent page views.
                                         *
                                         * @method
                                         */
                                        update: ( function () {
                                                var timer;

                                                function flush() {
                                                        var data,
                                                                key = mw.loader.store.getStoreKey();

                                                        if ( !mw.loader.store.enabled ) {
                                                                return false;
                                                        }
                                                        mw.loader.store.prune();
                                                        try {
                                                                // Replacing the content of the module store might fail if the new
                                                                // contents would exceed the browser's localStorage size limit. To
                                                                // avoid clogging the browser with stale data, always remove the old
                                                                // value before attempting to set the new one.
                                                                localStorage.removeItem( key );
                                                                data = JSON.stringify( mw.loader.store );
                                                                localStorage.setItem( key, data );
                                                        } catch ( e ) {
                                                                log( 'Storage error', e );
                                                        }
                                                }

                                                return function () {
                                                        clearTimeout( timer );
                                                        timer = setTimeout( flush, 2000 );
                                                };
                                        }() )
                                }
                        };
                }() ),

                /**
                 * HTML construction helper functions
                 *
                 *     @example
                 *
                 *     var Html, output;
                 *
                 *     Html = mw.html;
                 *     output = Html.element( 'div', {}, new Html.Raw(
                 *         Html.element( 'img', { src: '<' } )
                 *     ) );
                 *     mw.log( output ); // <div><img src="&lt;"/></div>
                 *
                 * @class mw.html
                 * @singleton
                 */
                html: ( function () {
                        function escapeCallback( s ) {
                                switch ( s ) {
                                        case '\'':
                                                return '&#039;';
                                        case '"':
                                                return '&quot;';
                                        case '<':
                                                return '&lt;';
                                        case '>':
                                                return '&gt;';
                                        case '&':
                                                return '&amp;';
                                }
                        }

                        return {
                                /**
                                 * Escape a string for HTML.
                                 *
                                 * Converts special characters to HTML entities.
                                 *
                                 *     mw.html.escape( '< > \' & "' );
                                 *     // Returns &lt; &gt; &#039; &amp; &quot;
                                 *
                                 * @param {string} s The string to escape
                                 * @return {string} HTML
                                 */
                                escape: function ( s ) {
                                        return s.replace( /['"<>&]/g, escapeCallback );
                                },

                                /**
                                 * Create an HTML element string, with safe escaping.
                                 *
                                 * @param {string} name The tag name.
                                 * @param {Object} attrs An object with members mapping element names to values
                                 * @param {Mixed} contents The contents of the element. May be either:
                                 *
                                 *  - string: The string is escaped.
                                 *  - null or undefined: The short closing form is used, e.g. `<br/>`.
                                 *  - this.Raw: The value attribute is included without escaping.
                                 *  - this.Cdata: The value attribute is included, and an exception is
                                 *    thrown if it contains an illegal ETAGO delimiter.
                                 *    See <http://www.w3.org/TR/1999/REC-html401-19991224/appendix/notes.html#h-B.3.2>.
                                 * @return {string} HTML
                                 */
                                element: function ( name, attrs, contents ) {
                                        var v, attrName, s = '<' + name;

                                        for ( attrName in attrs ) {
                                                v = attrs[attrName];
                                                // Convert name=true, to name=name
                                                if ( v === true ) {
                                                        v = attrName;
                                                // Skip name=false
                                                } else if ( v === false ) {
                                                        continue;
                                                }
                                                s += ' ' + attrName + '="' + this.escape( String( v ) ) + '"';
                                        }
                                        if ( contents === undefined || contents === null ) {
                                                // Self close tag
                                                s += '/>';
                                                return s;
                                        }
                                        // Regular open tag
                                        s += '>';
                                        switch ( typeof contents ) {
                                                case 'string':
                                                        // Escaped
                                                        s += this.escape( contents );
                                                        break;
                                                case 'number':
                                                case 'boolean':
                                                        // Convert to string
                                                        s += String( contents );
                                                        break;
                                                default:
                                                        if ( contents instanceof this.Raw ) {
                                                                // Raw HTML inclusion
                                                                s += contents.value;
                                                        } else if ( contents instanceof this.Cdata ) {
                                                                // CDATA
                                                                if ( /<\/[a-zA-z]/.test( contents.value ) ) {
                                                                        throw new Error( 'mw.html.element: Illegal end tag found in CDATA' );
                                                                }
                                                                s += contents.value;
                                                        } else {
                                                                throw new Error( 'mw.html.element: Invalid type of contents' );
                                                        }
                                        }
                                        s += '</' + name + '>';
                                        return s;
                                },

                                /**
                                 * Wrapper object for raw HTML passed to mw.html.element().
                                 * @class mw.html.Raw
                                 */
                                Raw: function ( value ) {
                                        this.value = value;
                                },

                                /**
                                 * Wrapper object for CDATA element contents passed to mw.html.element()
                                 * @class mw.html.Cdata
                                 */
                                Cdata: function ( value ) {
                                        this.value = value;
                                }
                        };
                }() ),

                // Skeleton user object. mediawiki.user.js extends this
                user: {
                        options: new Map(),
                        tokens: new Map()
                },

                /**
                 * Registry and firing of events.
                 *
                 * MediaWiki has various interface components that are extended, enhanced
                 * or manipulated in some other way by extensions, gadgets and even
                 * in core itself.
                 *
                 * This framework helps streamlining the timing of when these other
                 * code paths fire their plugins (instead of using document-ready,
                 * which can and should be limited to firing only once).
                 *
                 * Features like navigating to other wiki pages, previewing an edit
                 * and editing itself – without a refresh – can then retrigger these
                 * hooks accordingly to ensure everything still works as expected.
                 *
                 * Example usage:
                 *
                 *     mw.hook( 'wikipage.content' ).add( fn ).remove( fn );
                 *     mw.hook( 'wikipage.content' ).fire( $content );
                 *
                 * Handlers can be added and fired for arbitrary event names at any time. The same
                 * event can be fired multiple times. The last run of an event is memorized
                 * (similar to `$(document).ready` and `$.Deferred().done`).
                 * This means if an event is fired, and a handler added afterwards, the added
                 * function will be fired right away with the last given event data.
                 *
                 * Like Deferreds and Promises, the mw.hook object is both detachable and chainable.
                 * Thus allowing flexible use and optimal maintainability and authority control.
                 * You can pass around the `add` and/or `fire` method to another piece of code
                 * without it having to know the event name (or `mw.hook` for that matter).
                 *
                 *     var h = mw.hook( 'bar.ready' );
                 *     new mw.Foo( .. ).fetch( { callback: h.fire } );
                 *
                 * Note: Events are documented with an underscore instead of a dot in the event
                 * name due to jsduck not supporting dots in that position.
                 *
                 * @class mw.hook
                 */
                hook: ( function () {
                        var lists = {};

                        /**
                         * Create an instance of mw.hook.
                         *
                         * @method hook
                         * @member mw
                         * @param {string} name Name of hook.
                         * @return {mw.hook}
                         */
                        return function ( name ) {
                                var list = hasOwn.call( lists, name ) ?
                                        lists[name] :
                                        lists[name] = $.Callbacks( 'memory' );

                                return {
                                        /**
                                         * Register a hook handler
                                         * @param {Function...} handler Function to bind.
                                         * @chainable
                                         */
                                        add: list.add,

                                        /**
                                         * Unregister a hook handler
                                         * @param {Function...} handler Function to unbind.
                                         * @chainable
                                         */
                                        remove: list.remove,

                                        /**
                                         * Run a hook.
                                         * @param {Mixed...} data
                                         * @chainable
                                         */
                                        fire: function () {
                                                return list.fireWith.call( this, null, slice.call( arguments ) );
                                        }
                                };
                        };
                }() )
        };

        // Alias $j to jQuery for backwards compatibility
        // @deprecated since 1.23 Use $ or jQuery instead
        mw.log.deprecate( window, '$j', $, 'Use $ or jQuery instead.' );

        // Attach to window and globally alias
        window.mw = window.mediaWiki = mw;

        // Auto-register from pre-loaded startup scripts
        if ( $.isFunction( window.startUp ) ) {
                window.startUp();
                window.startUp = undefined;
        }

}( jQuery ) );