var speed=18//速度数值越大速度越慢
  demo22.innerHTML=demo21.innerHTML
  function Marquee3(){
  if(demo22.offsetWidth-demo20.scrollLeft<=0)
  demo20.scrollLeft-=demo21.offsetWidth
  else{
  demo20.scrollLeft++
  }
  }
  var MyMar3=setInterval(Marquee3,speed)
  demo20.onmouseover=function() {clearInterval(MyMar3)}
  demo20.onmouseout=function() {MyMar3=setInterval(Marquee3,speed)}