ui/webui/resources/js/event_tracker.js

   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 {{target: !EventTarget,
  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 EventTarget.addEventListener.
  43    * @param {!EventTarget} target The DOM target 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(target, eventType, listener, opt_capture) {
  49     var capture = !!opt_capture;
  50     var h = {
  51       target: target,
  52       eventType: eventType,
  53       listener: listener,
  54       capture: capture,
  55     };
  56     this.listeners_.push(h);
  57     target.addEventListener(eventType, listener, capture);
  58   },
  59
  60   /**
  61    * Remove any specified event listeners added with this EventTracker.
  62    * @param {!EventTarget} target The DOM target to remove a listener from.
  63    * @param {?string} eventType The type of event to remove.
  64    */
  65   remove: function(target, eventType) {
  66     this.listeners_ = this.listeners_.filter(function(h) {
  67       if (h.target == target && (!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.target.removeEventListener(h.eventType, h.listener, h.capture);
  92 };