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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 /**
      6  * @fileoverview EventTracker is a simple class that manages the addition and
      7  * removal of DOM event listeners. In particular, it keeps track of all
      8  * listeners that have been added and makes it easy to remove some or all of
      9  * them without requiring all the information again. This is particularly handy
     10  * when the listener is a generated function such as a lambda or the result of
     11  * calling Function.bind.
     12  */
     13 
     14 /**
     15  * The type of the internal tracking entry. TODO(dbeam): move this back to
     16  * EventTracker.Entry when https://github.com/google/closure-compiler/issues/544
     17  * is fixed.
     18  * @typedef {{node: !Node,
     19  *            eventType: string,
     20  *            listener: Function,
     21  *            capture: boolean}}
     22  */
     23 var EventTrackerEntry;
     24 
     25 /**
     26  * Create an EventTracker to track a set of events.
     27  * EventTracker instances are typically tied 1:1 with other objects or
     28  * DOM elements whose listeners should be removed when the object is disposed
     29  * or the corresponding elements are removed from the DOM.
     30  * @constructor
     31  */
     32 function EventTracker() {
     33   /**
     34    * @type {Array.<EventTrackerEntry>}
     35    * @private
     36    */
     37   this.listeners_ = [];
     38 }
     39 
     40 EventTracker.prototype = {
     41   /**
     42    * Add an event listener - replacement for Node.addEventListener.
     43    * @param {!Node} node The DOM node to add a listener to.
     44    * @param {string} eventType The type of event to subscribe to.
     45    * @param {EventListener|Function} listener The listener to add.
     46    * @param {boolean=} opt_capture Whether to invoke during the capture phase.
     47    */
     48   add: function(node, eventType, listener, opt_capture) {
     49     var capture = !!opt_capture;
     50     var h = {
     51       node: node,
     52       eventType: eventType,
     53       listener: listener,
     54       capture: capture,
     55     };
     56     this.listeners_.push(h);
     57     node.addEventListener(eventType, listener, capture);
     58   },
     59 
     60   /**
     61    * Remove any specified event listeners added with this EventTracker.
     62    * @param {!Node} node The DOM node to remove a listener from.
     63    * @param {?string} eventType The type of event to remove.
     64    */
     65   remove: function(node, eventType) {
     66     this.listeners_ = this.listeners_.filter(function(h) {
     67       if (h.node == node && (!eventType || (h.eventType == eventType))) {
     68         EventTracker.removeEventListener_(h);
     69         return false;
     70       }
     71       return true;
     72     });
     73   },
     74 
     75   /**
     76    * Remove all event listeners added with this EventTracker.
     77    */
     78   removeAll: function() {
     79     this.listeners_.forEach(EventTracker.removeEventListener_);
     80     this.listeners_ = [];
     81   }
     82 };
     83 
     84 /**
     85  * Remove a single event listener given it's tracking entry. It's up to the
     86  * caller to ensure the entry is removed from listeners_.
     87  * @param {EventTrackerEntry} h The entry describing the listener to remove.
     88  * @private
     89  */
     90 EventTracker.removeEventListener_ = function(h) {
     91   h.node.removeEventListener(h.eventType, h.listener, h.capture);
     92 };
     93