#

API Docs for: 3.10.3
Show: Inherited Protected Private Deprecated

# File: event/js/synthetic.js

    /**
     * Define new DOM events that can be subscribed to from Nodes.
     *
     * @module event
     * @submodule event-synthetic
     */
    var CustomEvent = Y.CustomEvent,
        DOMMap   = Y.Env.evt.dom_map,
        toArray  = Y.Array,
        YLang    = Y.Lang,
        isObject = YLang.isObject,
        isString = YLang.isString,
        isArray  = YLang.isArray,
        query    = Y.Selector.query,
        noop     = function () {};

    /**
     * <p>The triggering mechanism used by SyntheticEvents.</p>
     *
     * <p>Implementers should not instantiate these directly.  Use the Notifier
     * provided to the event's implemented <code>on(node, sub, notifier)</code> or
     * <code>delegate(node, sub, notifier, filter)</code> methods.</p>
     *
     * @class SyntheticEvent.Notifier
     * @constructor
     * @param handle {EventHandle} the detach handle for the subscription to an
     *              internal custom event used to execute the callback passed to
     *              on(..) or delegate(..)
     * @param emitFacade {Boolean} take steps to ensure the first arg received by
     *              the subscription callback is an event facade
     * @private
     * @since 3.2.0
     */
    function Notifier(handle, emitFacade) {
        this.handle     = handle;
        this.emitFacade = emitFacade;
    }

    /**
     * <p>Executes the subscription callback, passing the firing arguments as the
     * first parameters to that callback. For events that are configured with
     * emitFacade=true, it is common practice to pass the triggering DOMEventFacade
     * as the first parameter.  Barring a proper DOMEventFacade or EventFacade
     * (from a CustomEvent), a new EventFacade will be generated.  In that case, if
     * fire() is called with a simple object, it will be mixed into the facade.
     * Otherwise, the facade will be prepended to the callback parameters.</p>
     *
     * <p>For notifiers provided to delegate logic, the first argument should be an
     * object with a &quot;currentTarget&quot; property to identify what object to
     * default as 'this' in the callback.  Typically this is gleaned from the
     * DOMEventFacade or EventFacade, but if configured with emitFacade=false, an
     * object must be provided.  In that case, the object will be removed from the
     * callback parameters.</p>
     *
     * <p>Additional arguments passed during event subscription will be
     * automatically added after those passed to fire().</p>
     *
     * @method fire
     * @param e {EventFacade|DOMEventFacade|Object|any} (see description)
     * @param arg* {any} additional arguments received by all subscriptions
     * @private
     */
    Notifier.prototype.fire = function (e) {
        // first arg to delegate notifier should be an object with currentTarget
        var args     = toArray(arguments, 0, true),
            handle   = this.handle,
            ce       = handle.evt,
            sub      = handle.sub,
            thisObj  = sub.context,
            delegate = sub.filter,
            event    = e || {},
            ret;

        if (this.emitFacade) {
            if (!e || !e.preventDefault) {
                event = ce._getFacade();

                if (isObject(e) && !e.preventDefault) {
                    Y.mix(event, e, true);
                    args[0] = event;
                } else {
                    args.unshift(event);
                }
            }

            event.type    = ce.type;
            event.details = args.slice();

            if (delegate) {
                event.container = ce.host;
            }
        } else if (delegate && isObject(e) && e.currentTarget) {
            args.shift();
        }

        sub.context = thisObj || event.currentTarget || ce.host;
        ret = ce.fire.apply(ce, args);
        sub.context = thisObj; // reset for future firing

        // to capture callbacks that return false to stopPropagation.
        // Useful for delegate implementations
        return ret;
    };

    /**
     * Manager object for synthetic event subscriptions to aggregate multiple synths on the
     * same node without colliding with actual DOM subscription entries in the global map of
     * DOM subscriptions.  Also facilitates proper cleanup on page unload.
     *
     * @class SynthRegistry
     * @constructor
     * @param el {HTMLElement} the DOM element
     * @param yuid {String} the yuid stamp for the element
     * @param key {String} the generated id token used to identify an event type +
     *                     element in the global DOM subscription map.
     * @private
     */
    function SynthRegistry(el, yuid, key) {
        this.handles = [];
        this.el      = el;
        this.key     = key;
        this.domkey  = yuid;
    }

    SynthRegistry.prototype = {
        constructor: SynthRegistry,

        // A few object properties to fake the CustomEvent interface for page
        // unload cleanup.  DON'T TOUCH!
        type      : '_synth',
        fn        : noop,
        capture   : false,

        /**
         * Adds a subscription from the Notifier registry.
         *
         * @method register
         * @param handle {EventHandle} the subscription
         * @since 3.4.0
         */
        register: function (handle) {
            handle.evt.registry = this;
            this.handles.push(handle);
        },

        /**
         * Removes the subscription from the Notifier registry.
         *
         * @method _unregisterSub
         * @param sub {Subscription} the subscription
         * @since 3.4.0
         */
        unregister: function (sub) {
            var handles = this.handles,
                events = DOMMap[this.domkey],
                i;

            for (i = handles.length - 1; i >= 0; --i) {
                if (handles[i].sub === sub) {
                    handles.splice(i, 1);
                    break;
                }
            }

            // Clean up left over objects when there are no more subscribers.
            if (!handles.length) {
                delete events[this.key];
                if (!Y.Object.size(events)) {
                    delete DOMMap[this.domkey];
                }
            }
        },

        /**
         * Used by the event system's unload cleanup process.  When navigating
         * away from the page, the event system iterates the global map of element
         * subscriptions and detaches everything using detachAll().  Normally,
         * the map is populated with custom events, so this object needs to
         * at least support the detachAll method to duck type its way to
         * cleanliness.
         *
         * @method detachAll
         * @private
         * @since 3.4.0
         */
        detachAll : function () {
            var handles = this.handles,
                i = handles.length;

            while (--i >= 0) {
                handles[i].detach();
            }
        }
    };

    /**
     * <p>Wrapper class for the integration of new events into the YUI event
     * infrastructure.  Don't instantiate this object directly, use
     * <code>Y.Event.define(type, config)</code>.  See that method for details.</p>
     *
     * <p>Properties that MAY or SHOULD be specified in the configuration are noted
     * below and in the description of <code>Y.Event.define</code>.</p>
     *
     * @class SyntheticEvent
     * @constructor
     * @param cfg {Object} Implementation pieces and configuration
     * @since 3.1.0
     * @in event-synthetic
     */
    function SyntheticEvent() {
        this._init.apply(this, arguments);
    }

    Y.mix(SyntheticEvent, {
        Notifier: Notifier,
        SynthRegistry: SynthRegistry,

        /**
         * Returns the array of subscription handles for a node for the given event
         * type.  Passing true as the third argument will create a registry entry
         * in the event system's DOM map to host the array if one doesn't yet exist.
         *
         * @method getRegistry
         * @param node {Node} the node
         * @param type {String} the event
         * @param create {Boolean} create a registration entry to host a new array
         *                  if one doesn't exist.
         * @return {Array}
         * @static
         * @protected
         * @since 3.2.0
         */
        getRegistry: function (node, type, create) {
            var el     = node._node,
                yuid   = Y.stamp(el),
                key    = 'event:' + yuid + type + '_synth',
                events = DOMMap[yuid];

            if (create) {
                if (!events) {
                    events = DOMMap[yuid] = {};
                }
                if (!events[key]) {
                    events[key] = new SynthRegistry(el, yuid, key);
                }
            }

            return (events && events[key]) || null;
        },

        /**
         * Alternate <code>_delete()</code> method for the CustomEvent object
         * created to manage SyntheticEvent subscriptions.
         *
         * @method _deleteSub
         * @param sub {Subscription} the subscription to clean up
         * @private
         * @since 3.2.0
         */
        _deleteSub: function (sub) {
            if (sub && sub.fn) {
                var synth = this.eventDef,
                    method = (sub.filter) ? 'detachDelegate' : 'detach';

                this._subscribers = [];

                if (CustomEvent.keepDeprecatedSubs) {
                    this.subscribers = {};
                }

                synth[method](sub.node, sub, this.notifier, sub.filter);
                this.registry.unregister(sub);

                delete sub.fn;
                delete sub.node;
                delete sub.context;
            }
        },

        prototype: {
            constructor: SyntheticEvent,

            /**
             * Construction logic for the event.
             *
             * @method _init
             * @protected
             */
            _init: function () {
                var config = this.publishConfig || (this.publishConfig = {});

                // The notification mechanism handles facade creation
                this.emitFacade = ('emitFacade' in config) ?
                                    config.emitFacade :
                                    true;
                config.emitFacade  = false;
            },

            /**
             * <p>Implementers MAY provide this method definition.</p>
             *
             * <p>Implement this function if the event supports a different
             * subscription signature.  This function is used by both
             * <code>on()</code> and <code>delegate()</code>.  The second parameter
             * indicates that the event is being subscribed via
             * <code>delegate()</code>.</p>
             *
             * <p>Implementations must remove extra arguments from the args list
             * before returning.  The required args for <code>on()</code>
             * subscriptions are</p>
             * <pre><code>[type, callback, target, context, argN...]</code></pre>
             *
             * <p>The required args for <code>delegate()</code>
             * subscriptions are</p>
             *
             * <pre><code>[type, callback, target, filter, context, argN...]</code></pre>
             *
             * <p>The return value from this function will be stored on the
             * subscription in the '_extra' property for reference elsewhere.</p>
             *
             * @method processArgs
             * @param args {Array} parmeters passed to Y.on(..) or Y.delegate(..)
             * @param delegate {Boolean} true if the subscription is from Y.delegate
             * @return {any}
             */
            processArgs: noop,

            /**
             * <p>Implementers MAY override this property.</p>
             *
             * <p>Whether to prevent multiple subscriptions to this event that are
             * classified as being the same.  By default, this means the subscribed
             * callback is the same function.  See the <code>subMatch</code>
             * method.  Setting this to true will impact performance for high volume
             * events.</p>
             *
             * @property preventDups
             * @type {Boolean}
             * @default false
             */
            //preventDups  : false,

            /**
             * <p>Implementers SHOULD provide this method definition.</p>
             *
             * Implementation logic for subscriptions done via <code>node.on(type,
             * fn)</code> or <code>Y.on(type, fn, target)</code>.  This
             * function should set up the monitor(s) that will eventually fire the
             * event.  Typically this involves subscribing to at least one DOM
             * event.  It is recommended to store detach handles from any DOM
             * subscriptions to make for easy cleanup in the <code>detach</code>
             * method.  Typically these handles are added to the <code>sub</code>
             * object.  Also for SyntheticEvents that leverage a single DOM
             * subscription under the hood, it is recommended to pass the DOM event
             * object to <code>notifier.fire(e)</code>.  (The event name on the
             * object will be updated).
             *
             * @method on
             * @param node {Node} the node the subscription is being applied to
             * @param sub {Subscription} the object to track this subscription
             * @param notifier {SyntheticEvent.Notifier} call notifier.fire(..) to
             *              trigger the execution of the subscribers
             */
            on: noop,

            /**
             * <p>Implementers SHOULD provide this method definition.</p>
             *
             * <p>Implementation logic for detaching subscriptions done via
             * <code>node.on(type, fn)</code>.  This function should clean up any
             * subscriptions made in the <code>on()</code> phase.</p>
             *
             * @method detach
             * @param node {Node} the node the subscription was applied to
             * @param sub {Subscription} the object tracking this subscription
             * @param notifier {SyntheticEvent.Notifier} the Notifier used to
             *              trigger the execution of the subscribers
             */
            detach: noop,

            /**
             * <p>Implementers SHOULD provide this method definition.</p>
             *
             * <p>Implementation logic for subscriptions done via
             * <code>node.delegate(type, fn, filter)</code> or
             * <code>Y.delegate(type, fn, container, filter)</code>.  Like with
             * <code>on()</code> above, this function should monitor the environment
             * for the event being fired, and trigger subscription execution by
             * calling <code>notifier.fire(e)</code>.</p>
             *
             * <p>This function receives a fourth argument, which is the filter
             * used to identify which Node's are of interest to the subscription.
             * The filter will be either a boolean function that accepts a target
             * Node for each hierarchy level as the event bubbles, or a selector
             * string.  To translate selector strings into filter functions, use
             * <code>Y.delegate.compileFilter(filter)</code>.</p>
             *
             * @method delegate
             * @param node {Node} the node the subscription is being applied to
             * @param sub {Subscription} the object to track this subscription
             * @param notifier {SyntheticEvent.Notifier} call notifier.fire(..) to
             *              trigger the execution of the subscribers
             * @param filter {String|Function} Selector string or function that
             *              accepts an event object and returns null, a Node, or an
             *              array of Nodes matching the criteria for processing.
             * @since 3.2.0
             */
            delegate       : noop,

            /**
             * <p>Implementers SHOULD provide this method definition.</p>
             *
             * <p>Implementation logic for detaching subscriptions done via
             * <code>node.delegate(type, fn, filter)</code> or
             * <code>Y.delegate(type, fn, container, filter)</code>.  This function
             * should clean up any subscriptions made in the
             * <code>delegate()</code> phase.</p>
             *
             * @method detachDelegate
             * @param node {Node} the node the subscription was applied to
             * @param sub {Subscription} the object tracking this subscription
             * @param notifier {SyntheticEvent.Notifier} the Notifier used to
             *              trigger the execution of the subscribers
             * @param filter {String|Function} Selector string or function that
             *              accepts an event object and returns null, a Node, or an
             *              array of Nodes matching the criteria for processing.
             * @since 3.2.0
             */
            detachDelegate : noop,

            /**
             * Sets up the boilerplate for detaching the event and facilitating the
             * execution of subscriber callbacks.
             *
             * @method _on
             * @param args {Array} array of arguments passed to
             *              <code>Y.on(...)</code> or <code>Y.delegate(...)</code>
             * @param delegate {Boolean} true if called from
             * <code>Y.delegate(...)</code>
             * @return {EventHandle} the detach handle for this subscription
             * @private
             * since 3.2.0
             */
            _on: function (args, delegate) {
                var handles  = [],
                    originalArgs = args.slice(),
                    extra    = this.processArgs(args, delegate),
                    selector = args[2],
                    method   = delegate ? 'delegate' : 'on',
                    nodes, handle;

                // Can't just use Y.all because it doesn't support window (yet?)
                nodes = (isString(selector)) ?
                    query(selector) :
                    toArray(selector || Y.one(Y.config.win));

                if (!nodes.length && isString(selector)) {
                    handle = Y.on('available', function () {
                        Y.mix(handle, Y[method].apply(Y, originalArgs), true);
                    }, selector);

                    return handle;
                }

                Y.Array.each(nodes, function (node) {
                    var subArgs = args.slice(),
                        filter;

                    node = Y.one(node);

                    if (node) {
                        if (delegate) {
                            filter = subArgs.splice(3, 1)[0];
                        }

                        // (type, fn, el, thisObj, ...) => (fn, thisObj, ...)
                        subArgs.splice(0, 4, subArgs[1], subArgs[3]);

                        if (!this.preventDups ||
                            !this.getSubs(node, args, null, true))
                        {
                            handles.push(this._subscribe(node, method, subArgs, extra, filter));
                        }
                    }
                }, this);

                return (handles.length === 1) ?
                    handles[0] :
                    new Y.EventHandle(handles);
            },

            /**
             * Creates a new Notifier object for use by this event's
             * <code>on(...)</code> or <code>delegate(...)</code> implementation
             * and register the custom event proxy in the DOM system for cleanup.
             *
             * @method _subscribe
             * @param node {Node} the Node hosting the event
             * @param method {String} "on" or "delegate"
             * @param args {Array} the subscription arguments passed to either
             *              <code>Y.on(...)</code> or <code>Y.delegate(...)</code>
             *              after running through <code>processArgs(args)</code> to
             *              normalize the argument signature
             * @param extra {any} Extra data parsed from
             *              <code>processArgs(args)</code>
             * @param filter {String|Function} the selector string or function
             *              filter passed to <code>Y.delegate(...)</code> (not
             *              present when called from <code>Y.on(...)</code>)
             * @return {EventHandle}
             * @private
             * @since 3.2.0
             */
            _subscribe: function (node, method, args, extra, filter) {
                var dispatcher = new Y.CustomEvent(this.type, this.publishConfig),
                    handle     = dispatcher.on.apply(dispatcher, args),
                    notifier   = new Notifier(handle, this.emitFacade),
                    registry   = SyntheticEvent.getRegistry(node, this.type, true),
                    sub        = handle.sub;

                sub.node   = node;
                sub.filter = filter;
                if (extra) {
                    this.applyArgExtras(extra, sub);
                }

                Y.mix(dispatcher, {
                    eventDef     : this,
                    notifier     : notifier,
                    host         : node,       // I forget what this is for
                    currentTarget: node,       // for generating facades
                    target       : node,       // for generating facades
                    el           : node._node, // For category detach

                    _delete      : SyntheticEvent._deleteSub
                }, true);

                handle.notifier = notifier;

                registry.register(handle);

                // Call the implementation's "on" or "delegate" method
                this[method](node, sub, notifier, filter);

                return handle;
            },

            /**
             * <p>Implementers MAY provide this method definition.</p>
             *
             * <p>Implement this function if you want extra data extracted during
             * processArgs to be propagated to subscriptions on a per-node basis.
             * That is to say, if you call <code>Y.on('xyz', fn, xtra, 'div')</code>
             * the data returned from processArgs will be shared
             * across the subscription objects for all the divs.  If you want each
             * subscription to receive unique information, do that processing
             * here.</p>
             *
             * <p>The default implementation adds the data extracted by processArgs
             * to the subscription object as <code>sub._extra</code>.</p>
             *
             * @method applyArgExtras
             * @param extra {any} Any extra data extracted from processArgs
             * @param sub {Subscription} the individual subscription
             */
            applyArgExtras: function (extra, sub) {
                sub._extra = extra;
            },

            /**
             * Removes the subscription(s) from the internal subscription dispatch
             * mechanism.  See <code>SyntheticEvent._deleteSub</code>.
             *
             * @method _detach
             * @param args {Array} The arguments passed to
             *                  <code>node.detach(...)</code>
             * @private
             * @since 3.2.0
             */
            _detach: function (args) {
                // Can't use Y.all because it doesn't support window (yet?)
                // TODO: Does Y.all support window now?
                var target = args[2],
                    els    = (isString(target)) ?
                                query(target) : toArray(target),
                    node, i, len, handles, j;

                // (type, fn, el, context, filter?) => (type, fn, context, filter?)
                args.splice(2, 1);

                for (i = 0, len = els.length; i < len; ++i) {
                    node = Y.one(els[i]);

                    if (node) {
                        handles = this.getSubs(node, args);

                        if (handles) {
                            for (j = handles.length - 1; j >= 0; --j) {
                                handles[j].detach();
                            }
                        }
                    }
                }
            },

            /**
             * Returns the detach handles of subscriptions on a node that satisfy a
             * search/filter function.  By default, the filter used is the
             * <code>subMatch</code> method.
             *
             * @method getSubs
             * @param node {Node} the node hosting the event
             * @param args {Array} the array of original subscription args passed
             *              to <code>Y.on(...)</code> (before
             *              <code>processArgs</code>
             * @param filter {Function} function used to identify a subscription
             *              for inclusion in the returned array
             * @param first {Boolean} stop after the first match (used to check for
             *              duplicate subscriptions)
             * @return {EventHandle[]} detach handles for the matching subscriptions
             */
            getSubs: function (node, args, filter, first) {
                var registry = SyntheticEvent.getRegistry(node, this.type),
                    handles  = [],
                    allHandles, i, len, handle;

                if (registry) {
                    allHandles = registry.handles;

                    if (!filter) {
                        filter = this.subMatch;
                    }

                    for (i = 0, len = allHandles.length; i < len; ++i) {
                        handle = allHandles[i];
                        if (filter.call(this, handle.sub, args)) {
                            if (first) {
                                return handle;
                            } else {
                                handles.push(allHandles[i]);
                            }
                        }
                    }
                }

                return handles.length && handles;
            },

            /**
             * <p>Implementers MAY override this to define what constitutes a
             * &quot;same&quot; subscription.  Override implementations should
             * consider the lack of a comparator as a match, so calling
             * <code>getSubs()</code> with no arguments will return all subs.</p>
             *
             * <p>Compares a set of subscription arguments against a Subscription
             * object to determine if they match.  The default implementation
             * compares the callback function against the second argument passed to
             * <code>Y.on(...)</code> or <code>node.detach(...)</code> etc.</p>
             *
             * @method subMatch
             * @param sub {Subscription} the existing subscription
             * @param args {Array} the calling arguments passed to
             *                  <code>Y.on(...)</code> etc.
             * @return {Boolean} true if the sub can be described by the args
             *                  present
             * @since 3.2.0
             */
            subMatch: function (sub, args) {
                // Default detach cares only about the callback matching
                return !args[1] || sub.fn === args[1];
            }
        }
    }, true);

    Y.SyntheticEvent = SyntheticEvent;

    /**
     * <p>Defines a new event in the DOM event system.  Implementers are
     * responsible for monitoring for a scenario whereby the event is fired.  A
     * notifier object is provided to the functions identified below.  When the
     * criteria defining the event are met, call notifier.fire( [args] ); to
     * execute event subscribers.</p>
     *
     * <p>The first parameter is the name of the event.  The second parameter is a
     * configuration object which define the behavior of the event system when the
     * new event is subscribed to or detached from.  The methods that should be
     * defined in this configuration object are <code>on</code>,
     * <code>detach</code>, <code>delegate</code>, and <code>detachDelegate</code>.
     * You are free to define any other methods or properties needed to define your
     * event.  Be aware, however, that since the object is used to subclass
     * SyntheticEvent, you should avoid method names used by SyntheticEvent unless
     * your intention is to override the default behavior.</p>
     *
     * <p>This is a list of properties and methods that you can or should specify
     * in the configuration object:</p>
     *
     * <dl>
     *   <dt><code>on</code></dt>
     *       <dd><code>function (node, subscription, notifier)</code> The
     *       implementation logic for subscription.  Any special setup you need to
     *       do to create the environment for the event being fired--E.g. native
     *       DOM event subscriptions.  Store subscription related objects and
     *       state on the <code>subscription</code> object.  When the
     *       criteria have been met to fire the synthetic event, call
     *       <code>notifier.fire(e)</code>.  See Notifier's <code>fire()</code>
     *       method for details about what to pass as parameters.</dd>
     *
     *   <dt><code>detach</code></dt>
     *       <dd><code>function (node, subscription, notifier)</code> The
     *       implementation logic for cleaning up a detached subscription. E.g.
     *       detach any DOM subscriptions added in <code>on</code>.</dd>
     *
     *   <dt><code>delegate</code></dt>
     *       <dd><code>function (node, subscription, notifier, filter)</code> The
     *       implementation logic for subscription via <code>Y.delegate</code> or
     *       <code>node.delegate</code>.  The filter is typically either a selector
     *       string or a function.  You can use
     *       <code>Y.delegate.compileFilter(selectorString)</code> to create a
     *       filter function from a selector string if needed.  The filter function
     *       expects an event object as input and should output either null, a
     *       matching Node, or an array of matching Nodes.  Otherwise, this acts
     *       like <code>on</code> DOM event subscriptions.  Store subscription
     *       related objects and information on the <code>subscription</code>
     *       object.  When the criteria have been met to fire the synthetic event,
     *       call <code>notifier.fire(e)</code> as noted above.</dd>
     *
     *   <dt><code>detachDelegate</code></dt>
     *       <dd><code>function (node, subscription, notifier)</code> The
     *       implementation logic for cleaning up a detached delegate subscription.
     *       E.g. detach any DOM delegate subscriptions added in
     *       <code>delegate</code>.</dd>
     *
     *   <dt><code>publishConfig</code></dt>
     *       <dd>(Object) The configuration object that will be used to instantiate
     *       the underlying CustomEvent. See Notifier's <code>fire</code> method
     *       for details.</dd>
     *
     *   <dt><code>processArgs</code></dt
     *       <dd>
     *          <p><code>function (argArray, fromDelegate)</code> Optional method
     *          to extract any additional arguments from the subscription
     *          signature.  Using this allows <code>on</code> or
     *          <code>delegate</code> signatures like
     *          <code>node.on(&quot;hover&quot;, overCallback,
     *          outCallback)</code>.</p>
     *          <p>When processing an atypical argument signature, make sure the
     *          args array is returned to the normal signature before returning
     *          from the function.  For example, in the &quot;hover&quot; example
     *          above, the <code>outCallback</code> needs to be <code>splice</code>d
     *          out of the array.  The expected signature of the args array for
     *          <code>on()</code> subscriptions is:</p>
     *          <pre>
     *              <code>[type, callback, target, contextOverride, argN...]</code>
     *          </pre>
     *          <p>And for <code>delegate()</code>:</p>
     *          <pre>
     *              <code>[type, callback, target, filter, contextOverride, argN...]</code>
     *          </pre>
     *          <p>where <code>target</code> is the node the event is being
     *          subscribed for.  You can see these signatures documented for
     *          <code>Y.on()</code> and <code>Y.delegate()</code> respectively.</p>
     *          <p>Whatever gets returned from the function will be stored on the
     *          <code>subscription</code> object under
     *          <code>subscription._extra</code>.</p></dd>
     *   <dt><code>subMatch</code></dt>
     *       <dd>
     *           <p><code>function (sub, args)</code>  Compares a set of
     *           subscription arguments against a Subscription object to determine
     *           if they match.  The default implementation compares the callback
     *           function against the second argument passed to
     *           <code>Y.on(...)</code> or <code>node.detach(...)</code> etc.</p>
     *       </dd>
     * </dl>
     *
     * @method define
     * @param type {String} the name of the event
     * @param config {Object} the prototype definition for the new event (see above)
     * @param force {Boolean} override an existing event (use with caution)
     * @return {SyntheticEvent} the subclass implementation instance created to
     *              handle event subscriptions of this type
     * @static
     * @for Event
     * @since 3.1.0
     * @in event-synthetic
     */
    Y.Event.define = function (type, config, force) {
        var eventDef, Impl, synth;

        if (type && type.type) {
            eventDef = type;
            force = config;
        } else if (config) {
            eventDef = Y.merge({ type: type }, config);
        }

        if (eventDef) {
            if (force || !Y.Node.DOM_EVENTS[eventDef.type]) {
                Impl = function () {
                    SyntheticEvent.apply(this, arguments);
                };
                Y.extend(Impl, SyntheticEvent, eventDef);
                synth = new Impl();

                type = synth.type;

                Y.Node.DOM_EVENTS[type] = Y.Env.evt.plugins[type] = {
                    eventDef: synth,

                    on: function () {
                        return synth._on(toArray(arguments));
                    },

                    delegate: function () {
                        return synth._on(toArray(arguments), true);
                    },

                    detach: function () {
                        return synth._detach(toArray(arguments));
                    }
                };

            }
        } else if (isString(type) || isArray(type)) {
            Y.Array.each(toArray(type), function (t) {
                Y.Node.DOM_EVENTS[t] = 1;
            });
        }

        return synth;
    };