<!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>无标题文档</title>
<style>
body{margin:0;padding:0}
#div1{background: #F00 ;width:200px;height:200px;
position:relative;left:-200px}
#span1{background:#F93 ;width:50px;height:50px;
left:200px;top:75px;position:absolute}
</style>
<script>
window.onload=function(){
var oDiv=document.getElementById('div1');
oDiv.onmouseover=function(){
startMove(10,0);
};
oDiv.onmouseout=function(){
startMove1(-10,-200);
}
var timer=null;
function startMove(speed, iTarget){
var oDiv=document.getElementById('div1');
setInterval(function(){
if (oDiv.offsetLeft==iTarget){
clearInterval(timer);
}
else{
oDiv.style.left=oDiv.offsetLeft+speed+'px';
}
}
,30)
};
}
</script>
</head>
<body>
<div>
<div id="div1"><span id="span1">分享 </span></div>
</div>
</body>
</html>
timer= setInterval(function(){},30)，如果不写，你的定时器就一直是timer=null;