html文件
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
* {
margin: 0;
padding: 0;
}
ul {
list-style: none;
width: 1300px;
}
#box {
width: 1200px;
height: 400px;
border: 2px solid red;
margin: 100px auto;
}
#box li {
width: 240px;
height: 400px;
/*border: 1px solid #000;*/
float: left;
}
</style>
</head>
<body>
<div id="box">
<ul>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
</ul>
</div>
<script src="../jquery-1.12.4.js"></script>
<script>
$(function () {
var $li = $("#box li");
for (var i = 0; i < $li.length; i++) {
$li.eq(i).css("backgroundImage", "url(images/" + (i + 1) + ".jpg)");
}
//给所有的li注册鼠标经过事件
$li.mouseenter(function () {
$(this).stop().animate({width:800}).siblings().stop().animate({width:100});
}).mouseleave(function () {
$li.stop().animate({width:240});
});
});
</script>
</body>
</html>
原文：https://www.cnblogs.com/luwn/p/12741607.html