为何没有作用呢？求助
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script type="text/javascript" src="jquery-1.8.1.min.js" ></script>
<style type="text/css">
.box{
width: 500px;
margin: 0 auto;
}
.box img{
width: 300px;
height: 400px;
}
</style>
</head>
<body>
<div>
<img src="1.jpg" id="myimage"><br />
<input type="button" value="放大" id="max" />
<input type="button" value="缩小" id="min" />
</div>
<script type="text/javascript">
window.onload = function(){
var maxbtn =document.getElementById('max');
maxbtn.onclick =function(){
maxfun();
}
}
var img =document.getElementById('myimage');
function maxfun(){
var endwidth =img.width*1.3;
var maxtime =setInterval(function(){
img.width = img.width*1.05;
img.height = img.height*1.05;
},20);
}
</script>
</body>
</html>
