var speed3=20//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,speed3)
demo.onmouseover=function() {clearInterval(MyMar)}
demo.onmouseout=function() {MyMar=setInterval(Marquee,speed3)}