<!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>
<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>  
</head>
<body onLoad="createCode()">


    <script language="javascript" type="text/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");   
       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');//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++)   
       {   
        var charIndex = Math.floor(Math.random()*36);   
        code +=selectChar[charIndex];   
       }    
       if(checkCode)   
       {   
         checkCode.className="code";   
         checkCode.value = code;
         checkCode.blur();   
       }        
     }     
     function validate ()   {   
       var inputCode = document.getElementById("validCode").value;   
       if(inputCode.length <=0)   
       {   
           alert("请输入验证码！");   
       }   
       else if(inputCode.toUpperCase() != code )   
       {   
          alert("验证码输入错误！");   
          createCode();//刷新验证码   
       }   
       else   
       {   
         alert("^-^ OK");   
       }   
 }   
       
    </script>  
    <form  action="#">  
     <input  type="text"   id="validCode" />  
    <input type="text" onClick="createCode()" readonly="readonly" id="checkCode" class="unchanged" style="width: 80px;cursor:pointer"  /><br />  
    <input id="Button1"  onclick="validate();" type="button" value="确定" />    
</form>

</body>
</html>


 

从网上找了个js验证码的实例来留个笔记。。。

​​https://blog.51cto.com/u_2870645​​​