<html> <head> <title>纯字验证码</title> <meta http-equiv='content-type' content='text/html;charset=utf-8'/> <script type='text/javascript' src='https://www.jb51.net/jquery-1.7.2.js'></script> <script type='text/javascript'> 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,'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');//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='text/css'> #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> <div>验证码： <input type = "text" id = "input"/> <input type="button" title='点击更换验证码' /> <input type = "button" value = "验证" onclick = "validate()"/> </div> </body> </html>