简单的js验证码

转自:未找到

<script type ="text/javascript" language ="javascript">
     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];


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

     }

     function validate() {
         var inputCode = document.getElementById("input1").value;
         if (inputCode.length <= 0) {
             alert("请输入验证码!");
             return false;
         }
         else if (inputCode.toLowerCase() == code.toLowerCase()) {
             return true;
         }
         else {

             alert("验证码输入错误!");
             createCode(); //刷新验证码 
             return false;
         }

     }
     function validate_required() {

         if (validate()) {

             return true;
         }
         else {
             return false;
         }
     }    
      
     </script>

 

验证码:<input style="width:60px"  id="input1"   class="login_input"  />
           <input  onclick="createCode()" readonly="readonly" id="checkCode" style=" width:40px; background:"   />

           <input type="submit" class="dlbtn" value="登录" onclick="return validate_required(); "/>

初次进入页面没有验证码,点击才有,可用jquery  当页面加载完成时,自动点击一次

$(document).ready(function(){

$("#checkCode").click();

})