<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
*{
margin:0;
padding:0;
}
ul{
list-style: none;
}
ul li{
width:200px;
height: 80px;
background: red;
margin-bottom: 20px;
border: 4px solid black;
}
</style>
<script>
window.onload=function(){
var Lis = document.getElementsByTagName("li");
for (var i = 0 ; i<Lis.length;i++){
Lis[i].timer = null;
Lis[i].onmouseover = function(){
startMove(this,'width',400);
};
Lis[i].onmouseout = function(){
startMove(this,'width',200);
}
}
function startMove(obj,attr,target){
clearInterval(obj.timer);
obj.timer = setInterval(function(){
var icur = parseInt(getStyle(obj,attr));
var speed = (target - icur)/8;
speed = speed > 0 ? Math.floor(speed) : Math.ceil(speed);
if(icur == target){
clearInterval(obj.timer);
}else{
obj.style[attr] = icur + speed + "px";
}
},30)
}
function getStyle(obj,attr){
if(obj.currentStyle){
return obj.currentStyle[attr];
}else{
return getComputedStyle(obj,false)[attr];
}
}
}
</script>
</head>
<body>
<ul>
<li></li>
<li></li>
<li></li>
</ul>
</body>
</html>
