listener.js

// listener object for attaching functions to be called after events

/**
 * listener - Singleton.  used to subscribe to and fire events
 */
var listener = function(){
	/**
	 * @param {Object} evts the container for all event listeners
	 * @private
	 */
	var evts = {};

	/**
	 * listen - subscribe to events
	 * @param {String} evtName the name to be listening for
	 * @param {Function} method the function to be fired
	 * @param {Object} context the value for the 'this' object inside the function
	 */
	var listen = function(evtName,method,scope) {
		if(method && method.constructor == Function) {
			evts[evtName] = evts[evtName]||[];
			evts[evtName][evts[evtName].length] = {method:method,scope:scope};
		}
	};

	/**
	 * fire - call all the event handlers
	 * @param {String} evtName the name of the event listner to invoke
	 * @param {Object} args args.data contains data passed to function,
	 *  args.remove kills listener after it fires
	 */
	var fire = function(evtName,args) {
		args = args || [];
		if( evts.hasOwnProperty(evtName)) {
			var evt = evts[evtName].reverse();
			for(var i=evt.length;i--;) {
				try{
					evt[i].method.apply(evt[i].scope||[],(args.data||[]));
				}catch(e){
					if(args && args.data && args.data.push) {
						evt[i].method(args.data[0]);
					} else {
						evt[i].method();
					}
				}
			}
			if(args.remove) {kill(evtName);}
		}
	};
  
	/**
	 * listening - check if event is being listened for
	 * @param {String} evtName name of event to check on
	 */
	var listening = function(evtName){
		return !!evts[evtName];
	};
	
	/**
	 * kill - stop listening to event
	 * @param {String} evtName name of event to kill
	 */
	var kill = function(evtName){
		if(evts.hasOwnProperty(evtName)) {delete evts[evtName];}
	};

	// return the public functions
	return {listen:listen,fire:fire,kill:kill,listening:listening};
}();