timer = setInterval(mar,30);
        //鼠标移上去清除时钟
        box.onmouseover = function(event){
            clearInterval(timer);
            event.stopPropagation();
            //这里是阻止冒泡，不加要冒泡到body上面，鼠标在body上面就会clearInterval(timer);
            box.onmouseout = function(event){
                timer = setInterval(mar, 30);
             event.stopPropagation();
            }
        };
        //用jq方式写
        /*$(box).on(‘mouseover‘,function(){
            clearInterval(timer);
        })*/
//        $(box).mouseover(function(event){
//            clearInterval(timer);
//            event.stopPropagation();
//            $(box).mouseout(function(e){
//                timer = setInterval(mar,30);
//                e.stopPropagation();
//            })
//        });

真是奇怪，js可以，jq却开启了多个定时器，谁能解答一下