JavaScript Events

(function(Events) {
	
	var _listeners = {};
	
	Events.proxy = function(event, handler) {
		var proxyHandler = function(context) {
			Events.removeEventListener(event, proxyHandler);
			handler(context);
		};
		return proxyHandler;
	}
	
	Events.addEventListener = function(event, handler) {
		_listeners[event] = _listeners[event] || [];
		_listeners[event].push(handler);
	};
	
	Events.addWait = function(condition, event, handler) {
		if (condition()) {
			handler();
			return;
		}
		
		Events.addEventListener(event, Events.proxy(event, handler));
	};
	
	Events.removeEventListener = function(event, handler) {
		var len = _getListeners(event).length;
		for (var i = len; i >= 0; i--) {
			if (_listeners[event][i] === handler) {
				_listeners[event].splice(i, 1);
			}
		}
	};
	
	Events.dispatchEvent = function(event, context) {
		if (_listeners.hasOwnProperty(event)) {
			var listeners = _listeners[event].slice(0);
			for (var i = 0; i < listeners.length; i++) {
				listeners[i](context);
			}
		}
	};
	
	_getListeners = function(event) {
		return _listeners[event] || [];
	}
	
})(window.Events = window.Events || {});