SOURCE

// 发布订阅者模式 (模拟一个简单的事件池)

var Event = {
    // 添加事件回调: {type:[listener1, listener2]}
    _listeners: {},
    // 添加
    addEvent: function(type, fn) {
        if (typeof this._listeners[type] === "undefined") {
            this._listeners[type] = [];
        }
        if (typeof fn === "function") {
            this._listeners[type].push(fn);
        }
        return this;
    },
    // 触发
    fireEvent: function(type) {
        var arrayEvent = this._listeners[type];
        if (arrayEvent instanceof Array) {
            for (var i = 0, length = arrayEvent.length; i < length; i += 1) {
                if (typeof arrayEvent[i] === "function") {
                    // 执行事件回调函数
                    arrayEvent[i]({ type: type });
                }
            }
        }
        return this;
    },
    // 删除
    removeEvent: function(type, fn) {
        var arrayEvent = this._listeners[type];
        if (typeof type === "string" && arrayEvent instanceof Array) {
            if (typeof fn === "function") {
                // 清除当前type类型事件下对应fn方法
                for (var i = 0, length = arrayEvent.length; i < length; i += 1) {
                    if (arrayEvent[i] === fn) {
                        this._listeners[type].splice(i, 1);
                        break;
                    }
                }
            } else {
                // 如果仅仅参数type, 或参数fn邪魔外道，则所有type类型事件清除
                delete this._listeners[type];
            }
        }
        return this;
    }
};

Event.addEvent("alert", function() {
    console.log("弹出!");
});
Event.addEvent("alert", function() {
    console.log("弹出 !!!!");
});

// 触发自定义alert事件
Event.fireEvent("alert");