为什么清除定时器没有用，运动后停不下来
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>速度动画</title>
<style type="text/css">
div{margin:0; padding: 0;}
#div1{width: 200px;height: 200px;background: red;position: relative;left: -200px;top:0px;}
#share{width: 20px;height: 50px; position: absolute;left: 200px;top: 75px;background: blue;}
</style>
</head>
<body>
<div id="div1">
<span id="share">分享</span>
</div>
</body>
<script type="text/javascript">
window.onload=function(){
var oDiv=document.getElementById('div1');
oDiv.onmouseover=function(){
startMove();
}
}
var timer=null;
function startMove(){
var oDiv=document.getElementById('div1');
var timer=setInterval(function(){
if(oDiv.offsetLeft==0){
clearInterval(timer);
}
else{
oDiv.style.left=oDiv.offsetLeft+10+"px";
}
},30)
}
</script>
</html>
