求大神帮忙看看为什么没有移动进去？
<!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">
<style type="text/css">
body{margin:0px;
padding:0px;}
#div1{
width:200px;
height:300px;
background-color:red;
position:relative;
left:-200px;
top:75px;}
#div1 span{
background-color:blue;
position:absolute;
left:200px;
top:175px;}
</style>
<script>
window.onload=function(){
var ddiv=document.getElementById("div1");
ddiv.onmouseover=function(){
startMove();}
}
var timer=null;
function startMove(){
clearInterval(timer);
var ddiv=document.getElementById("div1");
timer=setInterval(function(){
if(ddiv.offsetLeft==0){
clearInterval(timer);}
else{
ddiv.style.left=ddiv.offsetLeft+10+"px";
}
},30);
}
ddiv.onmouseout=function(){
startMove1();}
function startMove1(){
clearInterval(timer);
var ddiv=document.getElementById("div1");
timer=setInterval(function(){
if(ddiv.offsetLeft==-200){
clearInterval(timer);}
else{
ddiv.style.left=ddiv.offsetLeft-10+"px";
}
},30);
}
</script>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>
<body>
<div id='div1'><span id='share'>分享</span></div>
</body>
</html>
