仿wp后台登录错误时左右晃动某一层

JavaScript, 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>jQuery晃动层</title>
<style type="text/css">
body { font: 12px Georgia, serif; }
a { text-decoration: none; }
#header{margin:50px auto}
#header p{text-align:center;font-size:16px;font-weight:bold}
#box{width:400px;height:200px;background-color:#ccc;text-align:center}
#footer{text-align:center;font-size:14px;position:absolute;bottom:50px}
</style>
<script type="text/javascript" src="http://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script>
<script type="text/javascript">
var box_left = 0;
$(document).ready(function () {
 box_left = ($(window).width() - $('#box').width()) / 2;
 $('#box,#footer').css({'left': box_left, 'position':'absolute'});
});
function shock()
{ 
 for (i = 1; i < 7; i++)
 {
 $('#box').animate({
 'left': '-=15'
 }, 3, function() {
 $(this).animate({
 'left': '+=30'
 }, 3, function() {
 $(this).animate({
 'left': '-=15'
 }, 3, function() {
 $(this).animate({
 'left': box_left
 }, 3, function() {
 // shock end
 });
 });
 });
 });
 }
}
</script>
</head>
<body>
<div id="header">
<p>仿wp后台登录错误时左右晃动某一层</p>
</div>
<div id="box"><a href="#" onclick="shock();return false;">单击我查看效果</a></div>
</body>
</html>

演示：jQuery晃动

该代码片段来自于: http://www.sharejs.com/codes/javascript/254