// JavaScript Document
var speed=30; //数字越大速度越慢
var tab=document.getElementById("demo");
var tab1=document.getElementById("demo1");
var tab2 = document.getElementById("demo2");
if (tab && tab1 && tab2) {
    tab2.innerHTML = tab1.innerHTML; //克隆demo1为demo2
    function Marquee() {
        if (tab2.offsetWidth - tab.scrollLeft <= 0)//当滚动至demo1与demo2交界时
            tab.scrollLeft -= tab1.offsetWidth //demo跳到最顶端
        else {
            tab.scrollLeft++
        }
    }
    var MyMar = setInterval(Marquee, speed);
    tab.onmouseover = function () { clearInterval(MyMar) }; //鼠标移上时清除定时器达到滚动停止的目的
    tab.onmouseout = function () { MyMar = setInterval(Marquee, speed) }; //鼠标移开时重设定时器
}