third_party/polymer/v1_0/components/more-routing/emitter.html

   1 <!--
   2 Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
   3 This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
   4 The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
   5 The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
   6 Code distributed by Google as part of the polymer project is also
   7 subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
   8 -->
   9 <script>
  10 (function(scope) {
  11 var MoreRouting = scope.MoreRouting = scope.MoreRouting || {};
  12 MoreRouting.Emitter = Object.create(null);  // Minimal set of properties.
  13
  14 /**
  15  * A dumb prototype that provides very simple event subscription.
  16  *
  17  * You are responsible for initializing `__listeners` as an array on objects
  18  * that make use of this.
  19  */
  20 Object.defineProperties(MoreRouting.Emitter, {
  21
  22   /**
  23    * Registers a callback that will be called each time any parameter managed by
  24    * this object (or its parents) have changed.
  25    *
  26    * @param {!Function} callback
  27    * @return {{close: function()}}
  28    */
  29   __subscribe: {
  30     value: function __subscribe(callback) {
  31       this.__listeners.push(callback);
  32
  33       return {
  34         close: this.__unsubscribe.bind(this, callback),
  35       };
  36     },
  37   },
  38
  39   /**
  40    * Unsubscribes a previously registered callback.
  41    *
  42    * @param {!Function} callback
  43    */
  44   __unsubscribe: {
  45     value: function __unsubscribe(callback) {
  46       var index = this.__listeners.indexOf(callback);
  47       if (index < 0) {
  48         console.warn(this, 'attempted unsubscribe of unregistered listener:', callback);
  49         return;
  50       }
  51       this.__listeners.splice(index, 1);
  52     },
  53   },
  54
  55   /**
  56    * Notifies subscribed callbacks.
  57    */
  58   __notify: {
  59     value: function __notify(key, value) {
  60       if (this.__silent) return;
  61       var args = Array.prototype.slice.call(arguments);
  62       // Notify listeners on parents first.
  63       var parent = Object.getPrototypeOf(this);
  64       if (parent && parent.__notify && parent.__listeners) {
  65         parent.__notify.apply(parent, args);
  66       }
  67
  68       this.__listeners.forEach(function(listener) {
  69         listener.apply(null, args);
  70       }.bind(this));
  71     },
  72   },
  73
  74 });
  75
  76 })(window);
  77 </script>