这代码哪里出错了,为什么会不断加快速度
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>demo</title>
<style type="text/css">
*{margin:0;padding:0;}
div{width:50px;
overflow:hidden;
height:50px;
}
ul{
height: 72px;
overflow:hidden;
border:1px solid #ccc;
}
</style>
</head>
<body>
<div>
<ul id="box">
<li>哈哈哈</li>
<li>ooooo</li>
<li>cccc</li>
<li>qqqqqqq</li>
</ul>
</div>
<script type="text/javascript">
var box=document.getElementById('box'),
marqueeSpeed=50,
marqueeTimeOut=2000,
timer=null;
box.innerHTML+=box.innerHTML;
function startMove(){
box.scrollTop++;
timer=setInterval("scrollUp()",50);
}
function scrollUp(){
if (box.scrollTop%18==0) {
clearInterval(timer);
setInterval("startMove()",2000);
}else{
box.scrollTop++;
if (box.scrollTop>=box.scrollHeight/2) {
box.scrollTop=0;
};
}
}
function getStyle(obj,attr){
if (obj.currentStyle) {
return obj.currentStyle[attr];
}else{
return getComputedStyle(obj,false)[attr];
}
}
setTimeout('startMove()',2000);
</script>
</body>
</html>
