var speed=15//速度数值越大速度越慢
  demo2.innerHTML=demo1.innerHTML
  function Marquee(){
  if(demo2.offsetWidth-demo.scrollLeft<=0)
  demo.scrollLeft-=demo1.offsetWidth
  else{
  demo.scrollLeft++
  }
  }
  var MyMar=setInterval(Marquee,speed)
  demo.onmouseover=function() {clearInterval(MyMar)}
  demo.onmouseout=function() {MyMar=setInterval(Marquee,speed)}// JavaScript Document