哪错了 ？？
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
<title></title>
<script type="text/javascript" src="http://libs.baidu.com/jquery/1.9.1/jquery.js"></script>
</head>
<body>
<input type="button" name="" value="btn" id="btn">
<p id="ps">hello wrold</p>
<script type="text/javascript">
$("#btn").on('click', function (e) {
$("#btn").prepend($("#ps").clone())
})
</script>
</body>
</html>$("body").prepend($("#ps").clone());$("ps").prepend($("#ps").clone());都行，就是btn不行
