third_party/polymer/v1_0/components-chromium/more-routing/emitter-extracted.js

   1
   2 (function(scope) {
   3 var MoreRouting = scope.MoreRouting = scope.MoreRouting || {};
   4 MoreRouting.Emitter = Object.create(null);  // Minimal set of properties.
   5
   6 /**
   7  * A dumb prototype that provides very simple event subscription.
   8  *
   9  * You are responsible for initializing `__listeners` as an array on objects
  10  * that make use of this.
  11  */
  12 Object.defineProperties(MoreRouting.Emitter, {
  13
  14   /**
  15    * Registers a callback that will be called each time any parameter managed by
  16    * this object (or its parents) have changed.
  17    *
  18    * @param {!Function} callback
  19    * @return {{close: function()}}
  20    */
  21   __subscribe: {
  22     value: function __subscribe(callback) {
  23       this.__listeners.push(callback);
  24
  25       return {
  26         close: this.__unsubscribe.bind(this, callback),
  27       };
  28     },
  29   },
  30
  31   /**
  32    * Unsubscribes a previously registered callback.
  33    *
  34    * @param {!Function} callback
  35    */
  36   __unsubscribe: {
  37     value: function __unsubscribe(callback) {
  38       var index = this.__listeners.indexOf(callback);
  39       if (index < 0) {
  40         console.warn(this, 'attempted unsubscribe of unregistered listener:', callback);
  41         return;
  42       }
  43       this.__listeners.splice(index, 1);
  44     },
  45   },
  46
  47   /**
  48    * Notifies subscribed callbacks.
  49    */
  50   __notify: {
  51     value: function __notify(key, value) {
  52       if (this.__silent) return;
  53       var args = Array.prototype.slice.call(arguments);
  54       // Notify listeners on parents first.
  55       var parent = Object.getPrototypeOf(this);
  56       if (parent && parent.__notify && parent.__listeners) {
  57         parent.__notify.apply(parent, args);
  58       }
  59
  60       this.__listeners.forEach(function(listener) {
  61         listener.apply(null, args);
  62       }.bind(this));
  63     },
  64   },
  65
  66 });
  67
  68 })(window);