jquery实现键盘左右翻页特效

<p>上一篇：<a id='pre' href='http://www.daimajiayuan.com/sitejs-17294-1.html'>一款随滚动条下滑左右渐入的页面布局</a> </p> <p>下一篇：<a id='next' href='http://www.daimajiayuan.com/sitejs-18339-1.html'>点击复选框添加或删除value值到input输入框中</a> </p> 

$(document).ready(function(){   var prevpage=$("#pre").attr("href");   var nextpage=$("#next").attr("href");   $("body").keydown(function(event){    if(event.keyCode==37 && prevpage!=undefined) location=prevpage;    if(event.keyCode==39 && nextpage!=undefined) location=nextpage;       });  });