js生成验证码并且判断

 <style type="text/css">
        .code
        {
            font-family: Arial;
            font-style: italic;
            color: Red;
            border: 0;
            padding: 2px 3px;
            letter-spacing: 3px;
            font-weight: bolder;
        }
        .unchanged
        {
            border: 0;
        }
    </style>
    <script type="text/javascript" src="img/jquery-1.5.1.min.js"></script>
    <script language="javascript" type="text/javascript">

        var code; //在全局 定义验证码
        var code2; //在全局 定义验证码
        function createCode() {
            code = "";
            var checkCode = document.getElementById("checkCode");
            function RndNum(n) {
                var rnd = "";
                for (var i = 0; i < n; i++)
                    rnd += Math.floor(Math.random() * 10);
                return rnd;
            }



            var num = RndNum(2);
            var num2 = RndNum(2);

            code = num + "+" + num2 + "=";
            code2 = parseInt(num) + parseInt(num2)

            if (checkCode) {
                checkCode.className = "code";
                checkCode.value = code;
            }

        }
    </script>
    <script type="text/javascript">
        $(document).ready(function () {

            $("#input1").blur(function () {
                var inputCode = document.getElementById("input1").value;
                if (inputCode.length <= 0) {
                    alert("请输入验证码！");
                }
                else if (inputCode != code2) {
                    alert("验证码输入错误！");
                    createCode(); //刷新验证码
                }
                else {
                    alert("^-^ OK");
                }
            });
        })
    </script>
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 <form action="#">
    &nbsp;<input type="text" id="input1" />
    <input type="text" onclick="createCode()" readonly="readonly" id="checkCode" class="unchanged" style="width: 80px;background: #660099"/><br />
    </form>