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();