Issue 3862 - Add EventEmitter class and implement in the FilterNotifier

lib/filterNotifier.js

Index: lib/filterNotifier.js
===================================================================
--- a/lib/filterNotifier.js
+++ b/lib/filterNotifier.js
@@ -20,37 +20,38 @@
  * messages about filter changes.
  */
 
-/**
- * List of registered listeners
- * @type function[]
- */
-let listeners = [];
+let {EventEmitter} = require("events");
+
+const CATCH_ALL = "__all";
 
 /**
  * This class allows registering and triggering listeners for filter events.
  * @class
  */
-let FilterNotifier = exports.FilterNotifier =
+exports.FilterNotifier =
 {
+  __proto__: new EventEmitter(),
+
   /**
    * Adds a listener
+   *
+   * @deprecated use FilterNotifier.on(action, callback)
    */
   addListener: function(/**function(action, item, newValue, oldValue)*/ listener)
   {
-    if (listeners.indexOf(listener) >= 0)
-      return;
-
-    listeners.push(listener);
+    let listeners = this._listeners[CATCH_ALL];
+    if (!listeners || listeners.indexOf(listener) == -1)
+      this.on(CATCH_ALL, listener);
   },
 
   /**
    * Removes a listener that was previosly added via addListener
+   *
+   * @deprecated use FilterNotifier.off(action, callback)
    */
   removeListener: function(/**function(action, item, newValue, oldValue)*/ listener)
   {
-    let index = listeners.indexOf(listener);
-    if (index >= 0)
-      listeners.splice(index, 1);
+    this.off(CATCH_ALL, listener);
   },
 
   /**
@@ -63,11 +64,11 @@
    *                 "filter.added", "filter.removed", "filter.moved",
    *                 "filter.disabled", "filter.hitCount", "filter.lastHit")
    * @param {Subscription|Filter} item item that the change applies to
+   * @deprecated use FilterNotifier.emit(action)
    */
   triggerListeners: function(action, item, param1, param2, param3)
   {
-    let list = listeners.slice();
-    for (let listener of list)
-      listener(action, item, param1, param2, param3);
+    this.emit(action, item, param1, param2, param3);
+    this.emit(CATCH_ALL, action, item, param1, param2, param3);
   }
 };