js 无缝滚屏

<div id=demo style=overflow:auto;height:180;width:200;background:#009900;color:#006600>
<table  align=top>
<tr>
<td id=demo1 valign=top>

<p>aaaaaaaaaaa</p>
<p>aaaaaaaaaaa</p>
<p>aaaaaaaaaaa</p>
<p>aaaaaaaaaaa</p>
<p>aaaaaaaaaaa</p>
<p>aaaaaaaaaaa</p>

</td>
</tr>
<tr>
<td id=demo2 valign=top></td>
</tr>
</table>

</div>
<script>
var speed=15
demo2.innerHTML=demo1.innerHTML//克隆demo1为demo2
function Marquee(){
//        console.log(demo2.offsetHeight-demo.scrollTop);
if(demo2.offsetHeight-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++  //如果是横向的 将 所有的 height top 改成 width left
}
}
var MyMar=setInterval(Marquee,speed)//设置定时器
demo.onmouseover=function() {clearInterval(MyMar)}//鼠标移上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
</script>