var speed=5;
var demo=document.getElementById("demo");
var demo1=document.getElementById("demo1");
var demo2=document.getElementById("demo2");
  demo2.innerHTML=demo1.innerHTML;
  function Marquee(){
  if(demo2.offsetWidth-demo.scrollLeft<=0)
  demo.scrollLeft-=demo1.offsetWidth;
  else{
  demo.scrollLeft++;
  }
  }
var MyMar = setInterval(Marquee,speed);        //设置定时器
demo.onmouseover = function(){clearInterval(MyMar)}    //鼠标经过时清除定时器达到滚动停止的目的
demo.onmouseout = function(){MyMar = setInterval(Marquee,speed)}