滚动条框那一节的问题

<script type="text/javascript">

 var area = document.getElementById('moocBox');

 var con1 = document.getElementById('con1');

 var con2 = document.getElementById('con2');

 var speed = 50;

 area.scrollTop = 0;

 con2.innerHTML = con1.innerHTML;

 function scrollUp(){

if(area.scrollTop >= con1.scrollHeight) {

area.scrollTop = 0;

}else{

  area.scrollTop ++; 

} 

}

var myScroll = setInterval("scrollUp()",speed);

area.onmouseover = function(){

clearInterval(myScroll);

}

area.onmouseout = function(){

myScroll = setInterval("scrollUp()",speed);

这里可不可以直接让area.onmouseout=myScroll，，为什么?前面已经定义了myScroll = setInterval("scrollUp()",speed), 

}

 </script>