JavaScript实现PC端四格密码输入框

<!DOCTYPE html>
<html>
 <head>
 <meta charset="UTF-8">
 <title>四个密码输入框</title>
 <script type="text/javascript" src="jquery.min.js" ></script>
 </head>
 <style type="text/css">
 input{
 width:40px;
 height:40px;
 text-align: center;
 font-size:22px;
 }
 </style>
 <body>
 支付密码
 <input type="password" name="pwd1" maxlength="1"/>
 <input type="password" name="pwd2" maxlength="1"/>
 <input type="password" name="pwd3" maxlength="1"/>
 <input type="password" name="pwd4" maxlength="1"/>
 </body>
 <script>
 //必须引入jquery才可以用
 //1：当输入框1输入1个字符后，自动切换光标到输入框2
 $(document).ready(function(){
 $("[name='pwd1']").bind("input",function(){
 if($(this).val().length==1){
 $("[name='pwd2']").focus();
 }
 })
 $("[name='pwd2']").bind("input",function(){
 if($(this).val().length==1){
 $("[name='pwd3']").focus();
 }else if($(this).val().length==0){
 $("[name='pwd1']").focus();
 }
 })
 $("[name='pwd3']").bind("input",function(){
 if($(this).val().length==1){
 $("[name='pwd4']").focus();
 }else if($(this).val().length==0){
 $("[name='pwd2']").focus();
 }
 })
 $("[name='pwd4']").bind("input",function(){
 if($(this).val().length==0){
 $("[name='pwd3']").focus();
 }
 
 })
 })
 </script>
</html>