这个类摘自： ASP.NET Ajax典型应用 一书
xmlhttp.js
function $() {
var elements = new Array();
for (var i = 0; i < arguments.length; i++) {
var element = arguments[i];
if (typeof element == 'string')
element = document.getElementById(element);
if (arguments.length == 1)
return element;
elements.push(element);
}
return elements;
}
//------------------------------------------------------------------------------------------
//封装XMLHTTP的Request类的代码
var Request = new Object();
//定义一个XMLHTTP的数组
Request.reqList = [];
//创建一个XMLHTTP对象，兼容不同的浏览器
function getAjax()
{
var ajax=false;
try
{
ajax = new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
try
{
ajax = new ActiveXObject("Microsoft.XMLHTTP");
}
catch (E)
{
ajax = false;
}
}
if (!ajax && typeof XMLHttpRequest!='undefined')
{
ajax = new XMLHttpRequest();
}
return ajax;
}
//封装XMLHTTP向服务器发送请求的操作
//url:向服务器请求的路径；method：请求的方法，即是GET还是POST；callback：当服务器成功返回结果时，调用的函数
//data：向服务器请求时附带的数据；urlencoded：url是否编码；callback2;当服务器返回错误时调用的函数
Request.send = function(url, method, callback, data, urlencoded, callback2)
{
var req=getAjax(); //得到一个XMLHTTP的实例
//当XMLHTTP的请求状态发生改变时调用
req.onreadystatechange = function()
{
// 当请求已经加载
if (req.readyState == 4)
{
// 当请求返回成功
if (req.status < 400)
{
// 当定义了成功回调函数时，执行成功回调函数
if(callback)
callback(req,data);
}
// 当请求返回错误
else
{
alert("当加载数据时发生错误 :\n" + req.status+ "/" + req.statusText);
//当定义了失败回调函数时，执行失败回调函数
if (callback2)
callback2(req,data);
}
//服务器已经进行了处理，更改界面提示信息
afterLoading();
//删除XMLHTTP，释放资源
try {
delete req;
req = null;
} catch (e) {}
}
}
//如果以POST方式回发服务器
if (method=="POST")
{
req.open("POST", url, true);
//请求需要编码
if (urlencoded)
req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
req.send(data);
Request.reqList.push(req);
}
//以GET方式请求
else
{
req.open("GET", url, true);
req.send(null);
Request.reqList.push(req);
}
//正在向服务器发送请求，页面显示正在加载的提示
loading();
return req;
}
//全部清除XMLHTTP数组元素，释放资源
Request.clearReqList = function()
{
var ln = Request.reqList.length;
for (var i=0; i<ln; i++) {
var req = Request.reqList[i];
if (req)
{
try
{
delete req;
} catch(e) {}
}
}
Request.reqList = [];
}
//进一步封装XMLHTTP以POST方式发送请求时的代码
//clear：是否清除XMLHTTP数组的所有元素；其他参数的意义参见Request.send
Request.sendPOST = function(url, data, callback, clear, callback2)
{
if (clear)
Request.clearReqList();
Request.send(url, "POST", callback, data, true, callback2);
}
//进一步封装XMLHTTP以GET方式发送请求时的代码
Request.sendGET = function(url, callback, args, clear, callback2)
{
if (clear)
Request.clearReqList();
return Request.send(url, "GET", callback, args, false, callback2);
}
//向服务器发送请求过程中，显示页面加载提示
function loading()
{
var div = $("loadingflag");
if(div)
div.style.display ="";
}
//服务器处理完成后，页面加载提示消失
function afterLoading()
{
var div = $("loadingflag");
if(div)
div.style.display ="none";
}
使用例子：
test.htm
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>无标题页</title>
<script src="xmlhttp.js" type="text/javascript"></script>
<script type="text/javascript">
function go()
{
var post="name="+$("txtName").value+"&pwd="+$("txtPwd").value;
Request.sendPOST("Handler.ashx",post,rec,null,null);
}
function rec(req,data)
{
var retext=req.responseText;
$("result").innerHTML=retext;
}
</script>
</head>
<body>
<div>用户名：<input type="text" id="txtName" /></div>
<div>密码：<input type="text" id="txtPwd" /></div>
<div><input type="button" id="btnOK" onclick="go()" value="提交" /><span id="result"></span></div>
<div id="loadingflag" style="display:none">数据提交中，请等待...</div>
</body>
</html>
Handler.ashx
<%@ WebHandler Language="C#" Class="Handler" %>
using System;
using System.Web;
public class Handler : IHttpHandler {
public void ProcessRequest (HttpContext context) {
context.Response.ContentType = "text/plain";
string name = context.Request.Params["name"].ToString();
string pwd = context.Request.Params["pwd"].ToString();
if (name != "gdjlc" && pwd != "gdjlc")
context.Response.Write("用户名或密码错误。");
else
context.Response.Write("正确，进入系统。");
}
public bool IsReusable {
get {
return false;
}
}
}