window.onload=function(){
  function getElement(id){
   return document.getElementById(id);
  } 
  var speed=30;//滚动速度
  var demo=getElement("demo");
  var demo2=getElement("demo2");
  var demo1=getElement("demo1");
  demo2.innerHTML=demo1.innerHTML//复制demo1中的图片到demo2中
  
  function Marqueeleft(){//向左滚动
   if(demo2.offsetWidth-demo.scrollLeft<=0)
    demo.scrollLeft-=demo1.offsetWidth
   else
    demo.scrollLeft++
  }
  
  function Marqueeright(){//向右滚动
   if(demo2.offsetWidth-demo.scrollLeft>=565)
    demo.scrollLeft+=demo1.offsetWidth
   else
    demo.scrollLeft--
  }
 
  var MyMar=setInterval(Marqueeleft,speed)//自动开始滚动
  Direction='Left';//设定初始方向为向左滚
  demo.onmouseover=function() {clearInterval(MyMar)}
  demo.onmouseout=function() {
   if(Direction=='Left'){
    MyMar=setInterval(Marqueeleft,speed)
   }else if(Direction=='Right'){
    MyMar=setInterval(Marqueeright,speed)
   }
  };
 }