jquery获取焦点和失去焦点

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script src='../jquery.js'></script>
<style>
   .hide{display:none}
   .test{background:green}
</style>
</head>
<body>
       <div id='test'>ttttt</div>
       <input type='text' id='adress' value='请输入' />
   <script>
   $(function(){
       $('#adress').focus(function(){
           var text=$(this).val();
           if(text=='请输入'){
               $(this).val('');
           }
       });
       $('#adress').blur(function(){
           var text=$(this).val();
           if(text==''){
               $(this).val('请输入');
           }
       });
   });
   </script>

</body>
</html>