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Unified Diff: lib/events.js

Issue 29338969: Issue 3862 - Add EventEmitter class and implement in the FilterNotifier (Closed)
Patch Set: Fixed typo in comment Created March 23, 2016, 4:23 p.m.
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Index: lib/events.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/events.js
@@ -0,0 +1,102 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2016 Eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+"use strict";
+
+/**
+ * Registers and emits named events.
+ *
+ * @constructor
+ */
+exports.EventEmitter = function()
+{
+ this._listeners = Object.create(null);
+};
+
+exports.EventEmitter.prototype = {
+ /**
+ * Adds a listener for the specified event name.
+ *
+ * @param {string} name
+ * @param {function} listener
+ */
+ on: function(name, listener)
+ {
+ if (name in this._listeners)
+ this._listeners[name].push(listener);
+ else
+ this._listeners[name] = [listener];
+ },
+
+ /**
+ * Removes a listener for the specified event name.
+ *
+ * @param {string} name
+ * @param {function} listener
+ */
+ off: function(name, listener)
+ {
+ let listeners = this._listeners[name];
+ if (listeners)
+ {
+ let idx = listeners.indexOf(listener);
+ if (idx != -1)
+ listeners.splice(idx, 1);
+ }
+ },
+
+ /**
+ * Adds a one time listener and returns a promise that
+ * is resolved the next time the specified event is emitted.
+ *
+ * @return {Promise}
+ */
+ once: function(name)
+ {
+ return new Promise(function(resolve)
+ {
+ let listener = function()
+ {
+ this.off(name, listener);
+ resolve();
+ }.bind(this);
+
+ this.on(name, listener);
+ }.bind(this));
+ },
+
+ /**
+ * Calls all previously added listeners for the given event name.
+ *
+ * @param {string} name
+ * @param {...*} [arg]
+ */
+ emit: function(name)
+ {
+ let listeners = this._listeners[name];
+ if (listeners)
+ {
+ let args = [];
+ for (let i = 1; i < arguments.length; i++)
+ args.push(arguments[i]);
+
+ let currentListeners = listeners.slice();
+ for (let listener of currentListeners)
+ listener.apply(null, args);
+ }
+ }
+};
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