获得Event对象

function getEvent(){     //同时兼容ie和ff的写法         if(document.all)    return window.event;                 func=getEvent.caller;                    while(func!=null){                 var arg0=func.arguments[0];             if(arg0){                 if((arg0.constructor==Event || arg0.constructor ==MouseEvent)                     || (typeof(arg0)=="object" && arg0.preventDefault && arg0.stopPropagation)){                         return arg0;                 }             }             func=func.caller;        }        return null; }