var demoStr = demo.offsetWidth
 var demoStr2 = demo1.offsetWidth

  var speed=20
  demo2.innerHTML=demo1.innerHTML
  demo3.innerHTML=demo1.innerHTML
  function Marquee(){
  if(demo2.offsetWidth-demo.scrollLeft<=0){//demo的一半宽度一定要比demo2.offsetWidth的宽度要宽
  demo.scrollLeft-=demo1.offsetWidth
  }else{
  demo.scrollLeft++
  }
  }
  var MyMar=setInterval(Marquee,speed)
  demo.onmouseover=function() {clearInterval(MyMar)}
  demo.onmouseout=function() {MyMar=setInterval(Marquee,speed)}