//得到事件

 function getEvent(evt){

     if (evt && typeof(evt) != "undefined") {

         var e = window.event || arguments.callee.caller.arguments[0];

         if (typeof(evt) != "undefined") {

             e = window.event || evt;

         }

         return e;

     } else {

         if(window.event)    {return window.event;}

         try {

             func = getEvent.caller;

             while(func!=null){

                 var arg0=func.arguments[0];

                 if(arg0){

                     if((arg0.constructor==Event || arg0.constructor ==MouseEvent

                         || arg0.constructor==KeyboardEvent)

                         ||(typeof(arg0)=="object" && arg0.preventDefault

                         && arg0.stopPropagation)){

                         return arg0;

                     }

                 }

                 func = func.caller;

             }

         } catch (e) {

             return null;

         }

         return null;

     }

 }

 //获取事件操作对象

 function getTarget(evt) {

     //var e = window.event || arguments.callee.caller.arguments[0]; //获取触发事件的源对象

     var e = getEvent(evt); //获取触发事件的源对象

     if (typeof(e) != "undefined") {

         try {

             var target =  (typeof(e.srcElement) != "undefined") && e.srcElement ? e.srcElement : e.target;

         } catch (ex) {

             target = null;

         }

     } else {

         target = null;

     }

     return target;

 }

//事件冒泡

function preventEvent() {

    //取消事件冒泡

    //var e = arguments.callee.caller.arguments[0] || event; //若省略此句，下面的e改为event，IE运行可以，但是其他浏览器就不兼容

    var e = getEvent(); //获取触发事件的源对象

    if (e && e.stopPropagation) {

        // this code is for Mozilla and Opera

        e.stopPropagation();

    } else if (window.event) {

        // this code is for IE

        window.event.cancelBubble = true;

    }

}