一个简单的ajax

function_test.js文件
/* *
 * @author Sam Lin
 * @date:February 14 ,2007
 * @contact: linsentong@126.com
  */
function  $()
{
     var  elements =   new  Array();
   
     for ( var  i  = 0 ;i  <  arguments.length;i ++ )
    {
       // 取得参数的每一个值
        var  element =  arguments[i];
        if (typeofelement  ==   ' string ' )
          element  = document.getElementById(element);
      
       // 如果只是一个参数则返回
       if (arguments.length  ==   1 )
          returnelement;
      
      elements.push(element);
    }
    returnelements;
}
// 初始化XMLHttpRequest
var  xmlHttp;
function  InitiateXMLHttpRequest()
{

    if (window.XMLHttpRequest)
    {
       xmlHttp  = new  window.XMLHttpRequest();
    }
     else
    {
        try
       {
          xmlHttp  = new  ActiveXObject( " Msxml2.XMLHTTP " );
       }
       catch (e){
           try {
             xmlHttp  = new  ActiveXObject( " Microsoft.XMLHTTP " );
          }
          catch (e)
          {
             xmlHttp  = false ;
          }
       }
    }
    returnxmlHttp;
}
function  CallServer(url)
{
    if (xmlHttp)
    {
      xmlHttp.open( " GET " ,url, true );
      xmlHttp.onreadystatechange  =  DoCallBack;
      xmlHttp.send( null );
    }
}
function  DoCallBack()
{
     var  msg  = $( " divMessage " ).innerHTML;
    if (xmlHttp.readyState  ==   4 )
    {
       msg  += " Callback the server successful!<br/>ResponseText: " + xmlHttp.responseText + " <br /> " ;
    }
     else
    {
       msg  += " State: " + xmlHttp.readyState  + " <br /> " ;
    }
}

<% @ Page Language = " C# "  ContentType = " text/html " ResponseEncoding = " gb2312 "   %>
<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >
< html  xmlns ="http://www.w3.org/1999/xhtml" >
< head >
< meta  http-equiv ="Content-Type"  content ="text/html;charset=gb2312"   />
< script  type ="text/javascript" src ="function_test.js" ></ script >
        < scripttype ="text/javascript" >
          functiontest()
          {
              var  objTest =  $( " txtName " );
            alert(objTest.value);
          }
           var  xmlHttp =  InitiateXMLHttpRequest();
         alert(xmlHttp);
          functionCallServer(url)
          {
             if (xmlHttp)
             {
                if ($( " txtName " ).value  ==   "" )
                {
                  alert( " 用户名不用为空! " );
                   return ;
                }
                 else
                {
                   url  += $( " txtName " ).value;
                }
               xmlHttp.open( " POST " ,url, true );
               xmlHttp.onreadystatechange  =  DoCallBack;
               xmlHttp.send( null );
             }
          }
       functionDoCallBack()
       {
         
           var  msg  = $( " divMessage " ).innerHTML;
           // msg ="HH";
           var  tmp  = "" ;
          if (xmlHttp.readyState  ==   4 )
          {
            document.getElementById( " results " ).innerHTML  = xmlHttp.responseText;
             msg  += " Callback the server successful!<br/>ResponseText: " + xmlHttp.responseText + " <br /> " ;
             tmp  += " Callback the server successful!<br/>ResponseText: " + xmlHttp.responseText + " <br /> " ;
          }
           else
          {
             msg  += " State: " + xmlHttp.readyState  + " <br /> " ;
             tmp += " State: " + xmlHttp.readyState  + " <br /> " ;
            
          }
         alert(msg);
       }
        // var sTemp= document.getElementById("spanMessage");
       // alert(sTemp.innerHTML);
      
       functionTest()
       {
         alert($( " lblMessage " ).innerHTML);
       }
       </ script >
< title > 无标题文档 </ title >
</ head >
< body  MS_POSITIONING ="GridLayout" >
        < formid ="Form1"  method ="post"  runat ="server" >
           < inputtype ="text"  id ="txtName"  name ="txtName" >   < input  type ="button" id ="btnOk"  name ="btnOk"  value ="OK" onclick ="javascript:test()" >
           < br />
           < inputtype ="button"  value ="CallBack"  id ="btnCallBack" onclick ="CallServer('http://localhost/ch33/sendCallBack.aspx?name=')"   />
           < divid ="divMessage" ></ div >
           < spanid ="spanMessage" > t </ span >
          < asp:Label  ID ="lblMessage" runat ="server" > OOO-- </ asp:Label >
           < inputtype ="button"  id ="btnTest"  value ="Test"  onclick ="Test()" />
       </ form >
        < div  id ="results" ></ div >
</ body >
</ html >

ajax.aspx.cs文件
Page_Load事件如下:
private   void  Page_Load( object  sender, System.EventArgs e)
       {
           // 在此处放置用户代码以初始化页面
          if (Request.QueryString[ " name " ]  ==   null )
          {
            Response.Write( " Sorry the programe is wrong! " );
          }
           else
          {
              string  name =  Request.QueryString[ " name " ].ToString();
            Response.Write( " Welcome to use callback : " + name);
         
            
          }