Evented JavaScript for the browser

This script adds the EventEmitter class to your browser.

So you can listen for and emit events from what ever objects you choose.

Version 2 deters from the NodeJS implementation slightly but it is lighter and faster.

The main thing it lacks is the emitting of a warning when you create over 10 listeners for an event.

Example

// Initialise the EventEmitter
var ee = new EventEmitter();

// Initialise the listener function
function myListener() {
	console.log('The foo event was emitted.');
}

// Add the listener
ee.addListener('foo', myListener);

// Emit the foo event
ee.emit('foo'); // The listener function is now called

// Remove the listener
ee.removeListener('foo', myListener);

// Log the array of listeners to show that it has been removed
console.log(ee.listeners('foo'));

Known bugs

I only know of one at the moment, you can not remove listeners assigned via once.

If you find any more, please put them in the issues section.

API

addListener(eventName, listener)

Assigns a listener to the specified event

• param {String} eventName Name of the event to assign the listener to
• param {Function} listener Function to be executed when the specified event is emitted
• returns {Object} The current instance of EventEmitter to allow chaining

on(eventName, listener)

Assigns a listener to the specified event (alias for addListener)

• param {String} eventName Name of the event to assign the listener to
• param {Function} listener Function to be executed when the specified event is emitted
• returns {Object} The current instance of EventEmitter to allow chaining

once(eventName, listener)

Assigns a listener to the specified event removes its self after the first run

• param {String} eventName Name of the event to assign the listener to
• param {Function} listener Function to be executed when the specified event is emitted
• returns {Object} The current instance of EventEmitter to allow chaining

emit(eventName)

Emits the specified event running all listeners associated with it

• param {String} eventName Name of the event to execute the listeners of
• param {Mixed} arguments You can pass as many arguments as you want after the event name. These will be passed to the listeners
• returns {Object} The current instance of EventEmitter to allow chaining

listeners(eventName)

Returns an array of listeners for the specified event name

• param {String} eventName Name of the event to get the listeners for
• returns {Array} An array of listeners for the specified event

removeListener(eventName, listener)

Removes the specified listener

• param {String} eventName Name of the event to remove the listener from
• param {Function} listener Listener function to be removed
• returns {Object} The current instance of EventEmitter to allow chaining

removeAllListeners(eventName)

Removes all listeners from the specified event

• param {String} eventName Name of the event to remove the listeners from
• returns {Object} The current instance of EventEmitter to allow chaining

Event: 'newListener'

Emitted whenever a new listener is added.

Passes the event name and listener that triggered it to the listeners.

Tests

EventEmitter is tested and working in the following browsers.

• Chrome
• Firefox
• Safari
• Opera
• IE 5 - 9

If you test it in something a little more obscure, please let me know how it turned out.

To test, simply run test.html in the test folder.

Author

Oliver Caldwell.

Licences

MIT

Copyright (C) 2011 Oliver Caldwell

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

GPL

Copyright (C) 2011 Oliver Caldwell

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program 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 this program. If not, see http://www.gnu.org/licenses/.