为什么这一段不能运行
var area=document.getElementById('box');
var con1=document.getElementById('con1');
var con2=document.getElementById('con2');;
var aa=50;
con2.innerHTML=con1.innerHTML;
function scrollUp(){
if(area.scrollTop>=con1.offsetHeight)
{
area.scrollTop=0; }
else{
area.scrollTop++;
}
}
var myScroll=setInterval('scrollUp()',aa);
