因为浏览器在加载js时会耗费时间，并且加载完成后会立即执行，当执行时其它资源有可能还未就绪，所以一般都会放在后面，保证第一屏界面迅速加载并呈现给访问者。
<!DOCTYPE html>
<html>
<head>
<title>Workdays</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="shortcut icon" href="/static/img/icon.png" type="image/x-icon" />
<link href="/static/lib/pure/1.0.0/pure-min.css" rel="stylesheet" type="text/css">
<link href="/static/css/index.css?v=1" rel="stylesheet" type="text/css">
</head>
<body>
<header>
...
</header>
...
<footer>
...
</footer>
<!-- start -->
<script type="text/javascript" src="/static/lib/require/require.js"></script>
<!-- common -->
<!-- modules -->
<!-- special -->
</body>
</html>