不能加载js文件，显示不出效果
<html>
<head><meta name="viewport" content="width-devise_width,initial-scale=1">
<title>canvas clock</title>
<style type="text/css">
div{
text-align:center;
margin-top:250px;
}
#clock{border: 1px solid #ccc;
}
</style>
</head>
<body>
<div><canvas id="clock" height="200px"width="200px"></canvas>
</div>
<script type="text/javascript" src="clock.js"></script>
</body>
</html>
