var speed3=25//速度数值越大速度越慢
document.getElementById("demo2").innerHTML=document.getElementById("demo1").innerHTML;

function Marquee(){
if(document.getElementById("demo2").offsetWidth-document.getElementById("demo").scrollLeft<=0)
document.getElementById("demo").scrollLeft-=document.getElementById("demo1").offsetWidth
else{
document.getElementById("demo").scrollLeft++
}
}

 var MyMar = setInterval(Marquee, speed3)
                            document.getElementById("demo").onmouseover = function() { clearInterval(MyMar) }
                            document.getElementById("demo").onmouseout = function() { MyMar = setInterval(Marquee, speed3) }