Event broadcasting that follows the on / off / trigger pattern

Events.js

/**

 Event broadcasting that follows the on / off / trigger pattern

 @arg obj:  optional object to extend with events. NOTE: this event system only listens to events sent with .trigger.
 dom events will not be listened for. To avoid confusion, you probably shouldn't use this on dom elements.

 var e = new Events();
 e.on("eventname", callbackFunc);   // add event listener
 e.off("eventname", callbackFunc);  // rm event listener
 e.off("eventname")                 // rm all event listeners

 e.trigger("eventname", data);      // trigger an event, passing data arg to all subscribed listeners

 // for convenience, you can keep reference to anonymous callback functions
 var cb = e.on("eventname", function(){...})
 */

Events = function (obj) {

	var events = obj || {}, // events object. new or existing
		listeners = {}; // keeps arrays of functions with a notification key

	events.debugEvents = false;

	events.on = function (event, callback) {
		if(events.debugEvents) console.log("Events."+"on()", arguments);
		// event will be the key that we retrieve the array of callbacks with
		if (listeners[event] == undefined) listeners[event] = [];

		// add to the beginning of the array so they'll be in order when we do a reverse while loop to process them
		listeners[event].unshift(callback);
		return callback;
	};

	events.off = function (event, callback) {
		if(events.debugEvents) console.log("Events."+"off()", arguments);
		try {
			if (callback != undefined) {
				// remove the callback
				var callbacks = listeners[event];
				var callbackIndex = callbacks.indexOf(callback);
				listeners[event].splice(callbackIndex, 1);
			} else {
				// remove all callbacks
				listeners[event] = undefined;
			}
		} catch (e) {
			// fail silently
		}
	};

	events.trigger = function (event, data) {
		if(events.debugEvents) console.log("Events.trigger", event);

		var callbacks = listeners[event] || [];

		var i = callbacks.length;
		while (i--) {
			callbacks[i](data);
		}

	};

	return events;

};