數字字母驗證
驗證碼：
<html>
<head>
<title>純字驗證碼</title>
<meta http-equiv='content-type' content='text/html;charset=utf-8'/>
<script type='text/javascript' src='jquery-1.7.2.js'></script>
<script type='text/javascript'>
var code ; //在全局定義驗證碼
function createCode(){
code = "";
var codeLength = 4;//驗證碼的長度
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');//隨機數
for(var i = 0; i < codeLength; i++) {//循環操作
var index = Math.floor(Math.random()*36);//取得隨機數的索引（0~35）
code += random[index];//根據索引取得隨機數加到code上
}
checkCode.value = code;//把code值賦給驗證碼
}
//校驗驗證碼
function validate(){
var inputCode = document.getElementById("input").value.toUpperCase(); //取得輸入的驗證碼並轉化為大寫
if(inputCode.length <= 0) { //若輸入的驗證碼長度為0
alert("請輸入驗證碼！"); //則彈出請輸入驗證碼
}else if(inputCode != code ) { //若輸入的驗證碼與產生的驗證碼不一致時
alert("驗證碼輸入錯誤！@_@"); //則彈出驗證碼輸入錯誤
createCode();//刷新驗證碼
document.getElementById("input").value = "";//清空文本框
}else { //輸入正確時
alert("合格！^-^");
}
}
</script>
<style type='text/css'>
#code{
font-family:Arial,宋體;
font-style:italic;
color:green;
border:0;
padding:2px 3px;
letter-spacing:3px;
font-weight:bolder;
}
</style>
</head>
<body onload='createCode()'>
<div>驗證碼：
<input type = "text" id = "input"/>
<input type="button" id="code" onclick="createCode()" style="width:60px" title='點擊更換驗證碼' />
<input type = "button" value = "驗證" onclick = "validate()"/>
</div>
</body>
</html>