// JavaScript Document
var demo = document.getElementById("demo");
var demo1 = document.getElementById("demo1");
var demo2 = document.getElementById("demo2");
var speed=40;    //滚动速度值，值越大速度越慢
var nnn=150/demo1.offsetHeight;
for(i=0;i<nnn;i++){demo1.innerHTML+="<br />"+ demo1.innerHTML}
demo2.innerHTML = demo1.innerHTML    //克隆demo2为demo1
function Marquee(){
    if(demo2.offsetTop-demo.scrollTop<=0)    //当滚动至demo1与demo2交界时
        demo.scrollTop-=demo1.offsetHeight    //demo跳到最顶端
    else{
        demo.scrollTop++
    }
}
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)}    //鼠标移开时重设定时器