<html> <head> <script language="javascript" type="text/javascript"> var code ; function createCode(){ code = new Array(); var codeLength = 4; var checkCode = document.getElementById("checkCode"); checkCode.value = ""; var selectChar = new Array(2,3,4,5,6,7,8,9,‘A‘,‘B‘,‘C‘,‘D‘,‘E‘,‘F‘,‘G‘,‘H‘,‘J‘,‘K‘,‘L‘,‘M‘,‘N‘,‘P‘,‘Q‘,‘R‘,‘S‘,‘T‘,‘U‘,‘V‘,‘W‘,‘X‘,‘Y‘,‘Z‘); for(var i=0;i<codeLength;i++) { var charIndex = Math.floor(Math.random()*32); code +=selectChar[charIndex]; } checkCode.value = code; } function validate () { var inputCode = document.getElementById("yzm").value.toUpperCase(); if(inputCode != code ){ alert("验证码错误！"); return false; } else { alert("验证码正确！"); return true; } } </script> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"> </head> <body onLoad="createCode();"> 验证码：<input type="text" id="yzm" size="5" /> <input type="button" id="checkCode" onClick="createCode()" title="刷新验证码" style="width:50px;color:#F00;border:0;letter-spacing:1px;font-family:Arial;" /> <input type="button" id="Button1" onClick="validate();" value="确定" /> </body> </html>
原文：http://www.cnblogs.com/vichin/p/7590266.html