使用JavaScript生成验证码-优快云博客

<%@ page language="java" pageEncoding="UTF-8"%>
<html>
<head>
<style type="text/css">
        .code
        {
            background-image:url(code.jpg);
            font-family:Arial;
            font-style:italic;
            color:Red;
            border:0;
            padding:2px 3px;
            letter-spacing:3px;
            font-weight:bolder;
        }
        .unchanged
        {
            border:0;
        }
    </style>
    <script language="javascript">
var code ; //在全局定义验证码
     function createCode()
     {
       code = "";
       var codeLength = 6;//验证码的长度
       var checkCode = document.getElementById("checkCode");   //获得id为checkcode的值
       var selectChar = new Array(0,1,2,3,4,5,6,7,8,9,'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','来');//所有候选组成验证码的字符，当然也可以用中文的

       for(var i=0;i<codeLength;i++)
       {   //获取一个随机数
        var charIndex = Math.floor(Math.random()*36);
       code +=selectChar[charIndex];


       }

       if(checkCode)
       { //如果这个数存在
         checkCode.className="code";
         checkCode.value = code;
       }

     }

      function validate(form)
       {
       var inputCode = document.getElementById("input1").value;

      if(inputCode != code )
       {
          alert("验证码为空或者输入错误！");
          createCode();//刷新验证码
          form.input1.focus();
          return false;
       }
       }
</script>
</head>
<title>js写的验证码</title>
<body onload="createCode()">
<form id="form" name="form" method="post" onsubmit="return validate(form)"
   action="admin.do?method=operatorLogin"/>
                验证码:
      <input type="text"   id="input1" /> <br />
      <input type="text" readonly="readonly" class="unchanged" style="width: 80px" id="checkCode"/><br />
      <input type="submit" width="20" name="Submit" value="提交" onclick="return checklog(form);"
         />
<a href="#" onclick="createCode()">换一张</a>
</form>
</body>
</html>

JS写的验证码