var speed=20; //数字越大速度越慢

var tab_1=document.getElementById("demo_a");
var tab1_1=document.getElementById("demo1_a");
var tab2_1=document.getElementById("demo2_a");
if(tab_1 != null)
{
    tab2_1.innerHTML=tab1_1.innerHTML; //克隆demo1为demo2
}
function Marquee_1(){
    if(tab2_1.offsetHeight-tab_1.scrollTop<=0)//当滚动至demo1与demo2交界时
        tab_1.scrollTop-=tab1_1.offsetHeight; //demo跳到最顶端
    else{
        tab_1.scrollTop++;
    }
}
if(tab_1 != null)
{
    var MyMar_1=setInterval(Marquee_1,speed);
    tab_1.onmouseover=function() {clearInterval(MyMar_1)};//鼠标移上时清除定时器达到滚动停止的目的
    tab_1.onmouseout=function() {MyMar_1=setInterval(Marquee_1,speed)};//鼠标移开时重设定时器
}




var tab_2=document.getElementById("demo_2");
var tab1_2=document.getElementById("demo1_2");
var tab2_2=document.getElementById("demo2_2");
if(tab_2 != null)
{
    tab2_2.innerHTML=tab1_2.innerHTML; //克隆demo1为demo2
}
function Marquee_2(){
    if(tab2_2.offsetHeight-tab_2.scrollTop<=0)//当滚动至demo1与demo2交界时
        tab_2.scrollTop-=tab1_2.offsetHeight; //demo跳到最顶端
    else{
        tab_2.scrollTop++;
    }
}
if(tab_2 != null)
{
    var MyMar_2=setInterval(Marquee_2,speed);
    tab_2.onmouseover=function() {clearInterval(MyMar_2)};//鼠标移上时清除定时器达到滚动停止的目的
    tab_2.onmouseout=function() {MyMar_2=setInterval(Marquee_2,speed)};//鼠标移开时重设定时器
}