//滚动速度设置，数越大越慢 
var speed=80; 
//demo2复制demo1的内容 
document.getElementById("demo2").innerHTML=document.getElementById("demo1").innerHTML; 
//滚动函数 
function Marquee() 
{ 
 if(document.getElementById("demo2").offsetTop-document.getElementById("demo").scrollTop<=0) 
  document.getElementById("demo").scrollTop-=document.getElementById("demo1").offsetHeight; 
 else 
  document.getElementById("demo").scrollTop++; 
} 
//滚动 
var MyMar=setInterval(Marquee,speed); 
//鼠标放上停止滚动 
document.getElementById("demo").onmouseover=function(){clearInterval(MyMar);} 
//鼠标离开继续滚动 
document.getElementById("demo").onmouseout=function(){MyMar=setInterval(Marquee,speed);}