因为已经走完了，需要克隆一个引进来，再继续，也就是说一共用两个，不断地来回交换滚动

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);