File: node/js/node-event-delegate.js

/**
 * Functionality to make the node a delegated event container
 * @module node
 * @submodule node-event-delegate
 */

/**
 * <p>Sets up a delegation listener for an event occurring inside the Node.
 * The delegated event will be verified against a supplied selector or
 * filtering function to test if the event references at least one node that
 * should trigger the subscription callback.</p>
 *
 * <p>Selector string filters will trigger the callback if the event originated
 * from a node that matches it or is contained in a node that matches it.
 * Function filters are called for each Node up the parent axis to the
 * subscribing container node, and receive at each level the Node and the event
 * object.  The function should return true (or a truthy value) if that Node
 * should trigger the subscription callback.  Note, it is possible for filters
 * to match multiple Nodes for a single event.  In this case, the delegate
 * callback will be executed for each matching Node.</p>
 *
 * <p>For each matching Node, the callback will be executed with its 'this'
 * object set to the Node matched by the filter (unless a specific context was
 * provided during subscription), and the provided event's
 * <code>currentTarget</code> will also be set to the matching Node.  The
 * containing Node from which the subscription was originally made can be
 * referenced as <code>e.container</code>.
 *
 * @method delegate
 * @param type {String} the event type to delegate
 * @param fn {Function} the callback function to execute.  This function
 *              will be provided the event object for the delegated event.
 * @param spec {String|Function} a selector that must match the target of the
 *              event or a function to test target and its parents for a match
 * @param context {Object} optional argument that specifies what 'this' refers to.
 * @param args* {any} 0..n additional arguments to pass on to the callback function.
 *              These arguments will be added after the event object.
 * @return {EventHandle} the detach handle
 * @for Node
 */
Y.Node.prototype.delegate = function(type) {

    var args = Y.Array(arguments, 0, true),
        index = (Y.Lang.isObject(type) && !Y.Lang.isArray(type)) ? 1 : 2;

    args.splice(index, 0, this._node);

    return Y.delegate.apply(Y, args);
};