话不多说，请看代码：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>不重复验证码</title> <style> .cont{width:300px;height:auto;margin:50px auto;} #useId{width:120px;height:45px;line-height:45px;background:#ccc;text-align:center;font-size:20px;margin:10px;} </style> </head> <body> <div> <div></div> <input type="text" /> <input type="button" value="Start" /> <div> <script> function $(id){ return document.getElementById(id); } var $useId = $('useId'), $txt = $('txt'), $btn = $('btn'); function getStr(){ var string = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', str = ''; while(str.length < 6){ var str1 = string.charAt(Math.round(Math.random() * 56)); if(str.indexOf(str1) === -1){ str += str1; } } $useId.innerHTML = str; } function checkCode(){ if($txt.value == $useId.innerHTML){ alert('验证成功'); }else{ alert('验证失败'); } } $useId.onclick = getStr; $btn.onclick = checkCode; </script> </body> </html>