JavaScirpt显示隐藏密码明文

<style>
#d2{position:relative; top:-18px; left:150px;}
</style> 
<!-------------------------------------------------!>
<div class="box">

   <div id="d1"><input type = "password" id="pwd"></div>
  <div id="d2"> <img src="open.bmp" id="eye" ></div>
 
</div>
<!-------------------------------------------------!>
<script>
var eye= document.getElementById('eye');
var pwd= document.getElementById('pwd');
var flag=0;
eye.onclick= function(){//每次单击， 修改flag的值
   if (flag==0){
     pwd.type='text';
     eye.src='open.bmp';
     flag=1; 
   }else {
     pwd.type='password';
     eye.src='close.bmp';
     flag=0; 
   };

};
</script>