又一個Ajax獲取xmlHTTPRequest代碼

 

var XMLHttp = {
_objPool: [],

_getInstance: function ()
{
for (var i = 0; i < this._objPool.length; i ++)
{
if (this._objPool[i].readyState == 0 || this._objPool[i].readyState == 4)
{
return this._objPool[i];
}
}

// IE5中不支持push方法
this._objPool[this._objPool.length] = this._createObj();

return this._objPool[this._objPool.length - 1];
},

_createObj: function ()
{
if (window.XMLHttpRequest)
{
var objXMLHttp = new XMLHttpRequest();

}
else
{
var MSXML = ['MSXML2.XMLHTTP.5.0', 'MSXML2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP', 'Microsoft.XMLHTTP'];
for(var n = 0; n < MSXML.length; n ++)
{
try
{
var objXMLHttp = new ActiveXObject(MSXML[n]);
break;
}
catch(e)
{
}
}
} 

// mozilla某些版本沒有readyState屬性
if (objXMLHttp.readyState == null)
{
objXMLHttp.readyState = 0;

objXMLHttp.addEventListener("load", function ()
{
objXMLHttp.readyState = 4;

if (typeof objXMLHttp.onreadystatechange == "function")
{
objXMLHttp.onreadystatechange();
}
}, false);
}

return objXMLHttp;
},

// 發送請求(方法[post,get], 地址, 數據, 回調函數)
sendReq: function (method, url, data, callback)
{
var objXMLHttp = this._getInstance();

with(objXMLHttp)
{
try
{
// 加隨機數防止緩存
if (url.indexOf("?") > 0)
{
url += "&randnum=" + Math.random();
}
else
{
url += "?randnum=" + Math.random();
}

open(method, url, true);

// 設定請求編碼方式
setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
send(data);
onreadystatechange = function ()
{
if (objXMLHttp.readyState == 4 && (objXMLHttp.status == 200 || objXMLHttp.status == 304))
{
callback(objXMLHttp);
}
}
}
catch(e)
{
alert(e);
}
}
}
};