js验证码

  $(function () {
            createCode();//加载时创建验证码
        });

        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("checkCode");
            var selectChar = 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‘);//所有候选组成验证码的字符，当然也可以用中文的

            for (var i = 0; i < codeLength; i++) {
                var charIndex = Math.floor(Math.random() * 36);
                code += selectChar[charIndex];
            }
           
            if (checkCode) {
                checkCode.className = "code";
                checkCode.innerHTML = code;
            }
        }

        //检查验证码是否通过
        function validate() {
            var inputCode = document.getElementById("txtValidCode").value;
            if (inputCode.length <= 0 && $("#labmeessage").text() == "") {
                $("#labmeessage").text(‘请输入验证码！‘);

            } else if (inputCode != code && $("#labmeessage").text() == "") {
                $("#labmeessage").text(‘验证码输入错误！！‘);
                createCode();//刷新验证码
            } else {

                // alert("登录成功！");
                save();
            }
        }

验证码：<input type="text" id="txtValidCode" style="width: 123px;" /><label onclick="createCode()" readonly="readonly" id="checkCode" class="unchanged" style="width: 51px;"></label></td>                   

  .code {
            font-family: Arial;
            font-style: italic;
            color: Red;
            border: 1px solid #A9A9A9;
            border-left: 0px;
            padding: 2px 3px;
            font-weight: bolder;
        }