EventEmitter.js

define([
	'../utilities/Map',
	'../common/proxy'
], function(Map, proxy){
	'use strict';

	var EventEmitter = function(){
		this.listeners = {};
	};

	EventEmitter.prototype.on = function(event, groupName, callback){
		var hasGroup = (arguments.length === 3);
		var group = hasGroup ? groupName : undefined;
		var fn = hasGroup ? callback : groupName;
		fn.__groupName = group;
		this.listeners[event] = this.listeners[event] || [];
		this.listeners[event].push(fn);
		return this;
	};

	EventEmitter.prototype.off = function(event, callback){
		var index, listeners = this.listeners[event];
		if(!listeners){
			return this;
		}
		if(arguments.length === 1){
			delete this.listeners[event];
			return this;
		}
		index = Map.indexOf(listeners, callback);
		listeners.splice(index, 1);
		if(listeners.length === 0){
			delete this.listeners[event];
		}
		return this;
	};

	EventEmitter.prototype.once = function(event, groupName, callback){
		var hasGroup = (arguments.length === 3);
		var group = hasGroup ? groupName : undefined;
		var fn = hasGroup ? callback : groupName;
		var on = proxy(function(){
			this.off(event, on);
			fn.apply(this, arguments);
		}, this);
		this.on(event, group, on);
		return this;
	};

	EventEmitter.prototype.trigger = function(event){
		var args = [].slice.call(arguments, 1);
		var listeners, index, total;
		var callbacks = this.listeners[event];
		var specialCallbacks = this.getWildcardListeners(event);
		if(callbacks){
			listeners = callbacks.slice();
			for(index = 0, total = listeners.length; index < total; ++index){
				if(listeners[index]){
					listeners[index].apply(this, args);
				}else{
					break;
				}
			}
		}
		if(specialCallbacks){
			listeners = specialCallbacks.slice();
			for(index = 0, total = listeners.length; index < total; ++index){
				if(listeners[index]){
					listeners[index].apply(this, [event].concat(args));
				}else{
					break;
				}
			}
		}
		return this;
	};

	EventEmitter.prototype.releaseGroup = function(groupName){
		for(var item in this.listeners){
			var handlers = this.listeners[item];
			for(var index = 0, total = handlers.length; index < total; index++){
				if(handlers[index].__groupName === groupName){
					handlers.splice(index, 1);
					index--;
					total--;
				}
			}
		}
		return this;
	};

	EventEmitter.prototype.getWildcardListeners = function(eventName){
		var result = [];
		for(var item in this.listeners){
			if(Object.prototype.hasOwnProperty.call(this.listeners, item)){
				var split = item.split('*');
				if (item === '*' || (split.length === 2 && eventName.slice(0, split[0].length) === split[0])){
					result = result.concat(this.listeners[item]);
				}
			}
		}
		return result;
	};

	return EventEmitter;
});

EventProxy.js

// Original: http://dean.edwards.name/my/events.js
function event(evt){
	evt.preventDefault = event.preventDefault;
	evt.stopPropagation = event.stopPropagation;
	return evt;
};

event.preventDefault = function(){
	this.returnValue = false;
};

event.stopPropagation = function(){
	this.cancelBubble = true;
};

var EventProxy = function(target){
	this.target = target||window;
	this.on.guid = 1;
};

EventProxy.prototype.on = function(event, callback){
	if(!this.target) return;
	if(this.target.addEventListener){
		this.target.addEventListener(event, callback, false);
	}else{
		callback.__guid = callback.__guid||this.on.guid++;
		this.target.events = this.target.events||{};
		if(!this.target.events[event]){
			this.target.events[event] = {};
			if(this.target['on'+ event]){
				this.target.events[event][0] = this.target['on'+ event];
			}
		}
		this.target.events[event][callback.__guid] = callback;
		this.target['on'+event] = this.on.notify;
	}
};

EventProxy.prototype.on.notify = function(evt){
	evt = evt || event(((this.ownerDocument||this.document||this).parentWindow||window).event);
	var key, listeners = this.events[evt.type];
	for(key in listeners){
		this.__notifier = listeners[key];
		if(this.__notifier(evt) === false){
			return false;
		}
	}
	return true;
};

EventProxy.prototype.off = function(event, callback){
	if(!this.target) return;
	if(this.target.removeEventListener){
		this.target.removeEventListener(event, callback);
	}else if(this.target.events && this.target.events[event]){
		delete this.target.events[event][callback.__guid];
	}
};

usage.js

window.onresize = function(){console.log('onResize from hell')};
var proxy = new EventProxy();
proxy.on('resize', arrange)
proxy.on('resize', resize)
proxy.off('resize', resize);
//proxy.off('resize', arrange);
function resize(evt){
	console.log('Redimensionando', evt);
}
function arrange(evt){
	console.log('Reorganizando', evt);
}