练习下自定义事件的实现，想让JS可以用AS3的语法使用自定义事件，实现很简单，因为没考虑复杂的情况吧。试过后发现有些地方还是模仿不了，最主要不一样的地方是：

1.侦听函数没法自动绑定那个函数所在的object，必须手动把object传进去，像这样：dispatcher.addEventListener(SampleDispatcher.ACTION, e.action, e);
最后还要传“e”这个obj进去，否则函数action里的this不指向e

2.使用的时候继承十分麻烦，还得小心翼翼，看demo就知道了。

//事件发送者类
var EventDispatcher = function() {
	this.listeners = {};
}
EventDispatcher.prototype = {
	addEventListener: function(type, fn, obj) {
		if (!fn) {
			throw new Error("function no found");
		}
		if (!this.listeners[type]) {
			this.listeners[type] = [];
		}
		var lis = this.listeners[type];
		if (!lis) {
			lis = [];
		}
		lis.push({"fn": fn, "obj": obj});
	},
	dispatchEvent: function(event) {
		var lis = this.listeners[event.type];
		if (lis && lis.length) {
			for (var i=0; i<lis.length; i++) {
				event.target = this;
				lis[i].fn.call(lis[i].obj, event)
			}
		}
	},
	removeEventListener: function(type, fn, obj) {
		var lis = this.listeners[type],
			ret = false;
		if (!lis) {
			return false;
		}
		for (var i=lis.length-1; i>-1; i--) {
			if (!fn || (lis[i].fn == fn && lis[i].obj == obj)) {
				delete lis[i];
				lis.splice(i, 1);
				ret = true;
			}
		}
		if (!lis.length) {
			delete this.listeners[type];
		}
		return ret;
	},
	hasEventListener: function(type) {
		var lis = this.listeners[type]
		return lis && lis.length > 0 ? true: false;
	}
}
//事件类
var Event = function(type) {
	this.type = type;
	this.target = null;
}
Event.prototype = {
	toString: function(){
		return this.type;
	},
	//clone功能未完善
	clone: function(){
		return new Event(this.type);
	}
}

完全仿照《Actionscript3殿堂之路》里事件发送和处理的例子，写了个demo:

//输出
var trace = function(msg) {
    document.write("<p>" + msg + "</p>");
}
//OrderEvent事件类
var OrderEvent = function(type) {
    OrderEvent.superclass.constructor.call(this, OrderEvent.ORDER_DISHES);
    this.dishes = [];
}
YAHOO.extend(OrderEvent, Event);
OrderEvent.ORDER_DISHES = "order";
//服务生Waiter类
var Waiter = function() {}
Waiter.prototype.replyOrderFood = function(event) {
    trace("你好," + event.target.name + "!你点的菜是:"+ event.dishes);
    trace("我马上吩咐厨房去做");
}
//客人类Customer
var Customer = function(name) {
    Customer.superclass.constructor.call(this);
    this.name = name;
}
YAHOO.extend(Customer, EventDispatcher);
Customer.prototype.order = function(dishes) {
    var orderDish = new OrderEvent();
    orderDish.dishes = dishes? dishes: ["农家小炒", "麻婆豆腐", "烤鱿鱼"];
    this.dispatchEvent(orderDish);
}
//生成客人和湘缘服务员
var bang = new Customer("bang"),
    xiangyuanWaiter = new Waiter();
//注册侦听器，讲服务员的replyOrderFood()方法注册为侦听“order”事件的侦听器
bang.addEventListener(OrderEvent.ORDER_DISHES, xiangyuanWaiter.replyOrderFood, xiangyuanWaiter);
//俺点菜了，菜单在俺这个类里面
bang.order();
//再点次菜，点些饮料
bang.order(["鸡尾酒","咖啡"]);
//吃完饭，移除侦听器
bang.removeEventListener(OrderEvent.ORDER_DISHES, xiangyuanWaiter.replyOrderFood, xiangyuanWaiter);

http://bangswork.googlecode.com/svn/trunk/AS3Event/Event.html