ajax 入門基礎(chǔ)之 XMLHttpRequest對象總結(jié)

var http_request= false;
function send_request(url)
{ ///初始化、指定處理函數(shù)、發(fā)送請求的函數(shù)

if (window.XMLHttpRequest) //Mozila
{
http_request = new XMLHttpRequest();
if (http_request.overrideMimeType)
{
http_request.overrideMimeType("text/xml");
}
}
else
if (window.ActiveXobject) //IE
{
try
{
http_request = new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
try{
http_request = new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e) { }
}
}

if (!http_request) // 異常，創(chuàng)建對象實例失敗
{
alert("不能創(chuàng)建XMLHttpRequest實例??！");
return false;
}
// 指定當(dāng)服務(wù)器返回信息時客戶端的處理方式
http_request.onreadystatechange = processRequest;
// SPAN twffan="done">確定發(fā)送請求的方式和URL以及是否同步執(zhí)行下段代碼
http_request.open("GET",url,true);
http_request.send(null);
}
//******************************************************************
function processRequest()
{
if (http_request.readyState == 4) // 判斷對象狀態(tài)
{
if (http_request.status == 200) // 請求結(jié)果已經(jīng)成功返回
{
alert(http_request.responseBody);
var a = document.getElementById("hh").innerText;
if (a =="1")
{
alert("不可用??！");
}
}
else //頁面不正常
{
alert("你請求的頁面不正常");
}
}
}
// ********************************************************************
function userCheck()
{
var f = document.Form1;
var userName = f.username.value;
if (userName == "")
{
alert("用戶名不能為空！！");
f.username.focus();
return false;
}
else
{
send_request("alert.aspx?username="+userName)
}
}