Ajax实现注册无刷新验证用户名是否存在

1. [代码][JavaScript]代码    

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    //创建一个方法来根据浏览器的版本 创建ajax对象

        function createxhr(){

            //如何进行方法的赛选

            if(window.XMLHttpRequest){

                var xhr = new XMLHttpRequest();

            } else {

                var version = ["Msxml2.XMLHTTP.6.0","Msxml2.XMLHTTP.5.0","Msxml2.XMLHTTP.4.0","Msxml2.XMLHTTP.3.0","Msxml2.XMLHTTP","Microsoft.XMLHTTP"];

                for(var i=0,len=version.length; i<len; i++){

                    var xhr = new ActiveXObject(version[i]);

                    if(xhr){

                        break;

                    }

                }

            }

            //返回ajax对象

            return xhr;

        }

        //dom模型

        function $(id){

            return document.getElementById(id);

        }

        //自动加载

        window.onload = function () {

            $('username').onblur = function (){

                var name = $('username').value;

//              alert(name);

                var xhr = createxhr();

 

                xhr.onreadystatechange = function (){

                    //判断状态

                    if(xhr.readyState == 4 ){

                        var res = $('res');

//                      alert(res);

                        res.innerHTML = xhr.responseText;

                    }

                }

                xhr.open('get','./data.php?username='+name,true);

                xhr.send(null);

            }

        }

 

 

 

代码][JavaScript]代码   

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//创建数据库连接     $link = mysql_connect('127.0.0.1','root','slops');     //选择数据库     mysql_select_db('test');     //设定客户端发送编码     mysql_query('set names utf8',$link);     //接受参数username     $username = $_GET['username'];         if(!empty($username)){             //sql语句查询user表中username字段             $sql = "select * from user where username ='$username'";         //  echo $sql;             $res = mysql_query($sql);             $result = mysql_num_rows($res);         //  var_dump($resu);die;             if($result>0){                 echo "该用户已存在,请从新选择用户名！！！".$username;             }                           else{                 echo "恭喜你，可以注册".$username;             }         }else{             echo "用户名不能为空";         }     mysql_close();