当没有传event 是时怎么去获取 事件对象

 
EventUtil.getEvent=function(e) {
            e = e || window.event;
            if (!e) {
                var c = this.getEvent.caller;
                while (c) {
                    e = c.arguments[0];
                    if (e && Event == e.constructor) {
                        break;
                    }
                    c = c.caller;
                }
            }
            return e;
}

 代码很简单我就不多介绍了。。关键在于  caller;