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js implementation of random number and letter verification code example code

怪我咯Original: 2017-07-13 15:12:572643browse

CAPTCHA (CAPTCHA) is the abbreviation of "Completely Automated Public Turing test to tell Computers and Humans Apart". It is a method to distinguish between users and computers. It is also a public fully automatic program for people. It can prevent: malicious cracking of passwords, ticket fraud, forum flooding, and effectively prevents a hacker from using a specific program to violently crack a specific registered user from making continuous login attempts. In fact, using verification codes is a common method for many websites now. We use This function is implemented in a relatively simple way. This question can be generated and judged by a computer, but only a human can answer it. Since computers cannot answer CAPTCHA questions, the user who answers the questions can be considered a human. This article mainly introduces the implementation code of js random verification code in detail. The specific content is as followsVerification code:

<html> 
  <head> 
    <title>纯字验证码</title> 
    <meta http-equiv=&#39;content-type&#39; content=&#39;text/html;charset=utf-8&#39;/> 
    <script type=&#39;text/javascript&#39; src=&#39;jquery-1.7.2.js&#39;></script> 
    <script type=&#39;text/javascript&#39;> 
    var code ; //在全局定义验证码  
      
    function createCode(){ 
       code = "";  
       var codeLength = 4;//验证码的长度  
       var checkCode = document.getElementById("code");  
       var random = new Array(0,1,2,3,4,5,6,7,8,9,&#39;A&#39;,&#39;B&#39;,&#39;C&#39;,&#39;D&#39;,&#39;E&#39;,&#39;F&#39;,&#39;G&#39;,&#39;H&#39;,&#39;I&#39;,&#39;J&#39;,&#39;K&#39;,&#39;L&#39;,&#39;M&#39;,&#39;N&#39;,&#39;O&#39;,&#39;P&#39;,&#39;Q&#39;,&#39;R&#39;,  
       &#39;S&#39;,&#39;T&#39;,&#39;U&#39;,&#39;V&#39;,&#39;W&#39;,&#39;X&#39;,&#39;Y&#39;,&#39;Z&#39;);//随机数  
       for(var i = 0; i < codeLength; i++) {//循环操作  
        var index = Math.floor(Math.random()*36);//取得随机数的索引（0~35）  
        code += random[index];//根据索引取得随机数加到code上  
      }  
      checkCode.value = code;//把code值赋给验证码  
    } 
    //校验验证码  
    function validate(){  
      var inputCode = document.getElementById("input").value.toUpperCase(); //取得输入的验证码并转化为大写     
      if(inputCode.length <= 0) { //若输入的验证码长度为0  
        alert("请输入验证码！"); //则弹出请输入验证码  
      }else if(inputCode != code ) { //若输入的验证码与产生的验证码不一致时  
        alert("验证码输入错误！@_@"); //则弹出验证码输入错误  
        createCode();//刷新验证码  
        document.getElementById("input").value = "";//清空文本框  
      }else { //输入正确时  
        alert("合格！^-^"); 
      } 
    } 
    </script> 
    <style type=&#39;text/css&#39;> 
    #code{ 
      font-family:Arial,宋体; 
      font-style:italic; 
      color:green; 
      border:0; 
      padding:2px 3px; 
      letter-spacing:3px; 
      font-weight:bolder; 
    } 
    </style> 
  </head> 
  <body onload=&#39;createCode()&#39;> 
    <p>验证码：  
      <input type = "text" id = "input"/>  
      <input type="button" id="code" onclick="createCode()" style="width:60px" title=&#39;点击更换验证码&#39; /> 
      <input type = "button" value = "验证" onclick = "validate()"/> 
    </p>  
  </body> 
</html>

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