js怎么控制我这个div里的图片放大缩小
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>周海的个人网站</title>
<meta name="viewport" content="width=device-width,initial-scale=1"/>
<link rel="stylesheet" href="styles.css">
<base target="_blank">
<style type="text/css">
body{
background:url("imges/background.jpg");
background-repeat:no-repeat;
background-size:100% 100%;
background-position-x:50%;
}
</style>
</head>
<body >
<div class="header">
<a class="logo" ><img src="imges/logo.png" ></a>
<p class="font"> Manifest oneself </p>
</div>
<div class="nav">
<ul>
<li><a href="#">首页</a></li>
<li><a href="#">素描</a></li>
<li><a href="#">油画</a></li>
<li><a href="#">水粉</a></li>
<li><a href="#">水彩</a></li>
<li><a href="#">速写</a></li>
<li><a href="#">同学回忆录</a></li>
</ul>
</div>
<div id="bob">
<img src="imges/01.jpg" width="200" height="200">
<img src="imges/02.jpg" width="200" height="200">
<img src="imges/03.jpg" width="200" height="200">
<img src="imges/04.jpg" width="200" height="200">
<img src="imges/05.jpg" width="200" height="200">
<img src="imges/06.jpg" width="200" height="200">
<img src="imges/07.jpg" width="200" height="200">
<img src="imges/08.jpg" width="200" height="200">
</div>
<script type="text/javascript" src="test.js"></script>
</body>
</html>
