创建元素节点，这里的return有什么作用，可以不用么
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
</head>
<body>
<script type="text/javascript">
var main1 = document.body;
//创建链接
function createa(url,text)
{
var alink = document.createElement("a");
alink.setAttribute("href",url);
alink.innerHTML=text;
return alink;
}
// 调用函数创建链接
main1.appendChild(createa("http://www.imooc.com","慕课网"));
</script>
</body>
</html>
