建一个XMLHttpRequest对象池
在ajax应用中，通常一个页面要同时发送多个请求，如果只有一个XMLHttpRequest对象，前面的请求还未完成，后面的就会把前面的覆盖掉，如果每次都创建一个新的XMLHttpRequest对象，也会造成浪费。解决的办法就是创建一个XMLHttpRequset的对象池，如果池里有空闲的对象，则使用此对象，否则将创建一个新的对象。
/**
* XMLHttpRequest Object Pool
*
* @author legend <legendsky@hotmail.com>
* @link http://www.ugia.cn/?p=85
* @Copyright www.ugia.cn
*/
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某些版本没有readyState属性
if (objXMLHttp.readyState == null)
{
objXMLHttp.readyState = 0;
objXMLHttp.addEventListener("load", function ()
{
objXMLHttp.readyState = 4;
if (typeof objXMLHttp.onreadystatechange == "function")
{
objXMLHttp.onreadystatechange();
}
}, false);
}
return objXMLHttp;
},
// 发送请求(方法[post,get], 地址, 数据, 回调函数)
sendReq: function (method, url, data, callback)
{
var objXMLHttp = this._getInstance();
with(objXMLHttp)
{
try
{
// 加随机数防止缓存
if (url.indexOf("?") > 0)
{
url += "&randnum=" + Math.random();
}
else
{
url += "?randnum=" + Math.random();
}
open(method, url, true);
// 设定请求编码方式
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);
}
}
}
};
* XMLHttpRequest Object Pool
*
* @author legend <legendsky@hotmail.com>
* @link http://www.ugia.cn/?p=85
* @Copyright www.ugia.cn
*/
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某些版本没有readyState属性
if (objXMLHttp.readyState == null)
{
objXMLHttp.readyState = 0;
objXMLHttp.addEventListener("load", function ()
{
objXMLHttp.readyState = 4;
if (typeof objXMLHttp.onreadystatechange == "function")
{
objXMLHttp.onreadystatechange();
}
}, false);
}
return objXMLHttp;
},
// 发送请求(方法[post,get], 地址, 数据, 回调函数)
sendReq: function (method, url, data, callback)
{
var objXMLHttp = this._getInstance();
with(objXMLHttp)
{
try
{
// 加随机数防止缓存
if (url.indexOf("?") > 0)
{
url += "&randnum=" + Math.random();
}
else
{
url += "?randnum=" + Math.random();
}
open(method, url, true);
// 设定请求编码方式
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);
}
}
}
};
示例：
<script type="text/javascript" src="xmlhttp.js"></script>
<script type="text/javascript">
function test(obj)
{
alert(obj.statusText);
}
XMLHttp.sendReq('GET', 'http://www.ugia.cn/wp-data/test.htm', '', test);
XMLHttp.sendReq('GET', 'http://www.ugia.cn/wp-data/test.htm', '', test);
XMLHttp.sendReq('GET', 'http://www.ugia.cn/wp-data/test.htm', '', test);
XMLHttp.sendReq('GET', 'http://www.ugia.cn/wp-data/test.htm', '', test);
alert('Pool length:' + XMLHttp._objPool.length);
</script>
<script type="text/javascript">
function test(obj)
{
alert(obj.statusText);
}
XMLHttp.sendReq('GET', 'http://www.ugia.cn/wp-data/test.htm', '', test);
XMLHttp.sendReq('GET', 'http://www.ugia.cn/wp-data/test.htm', '', test);
XMLHttp.sendReq('GET', 'http://www.ugia.cn/wp-data/test.htm', '', test);
XMLHttp.sendReq('GET', 'http://www.ugia.cn/wp-data/test.htm', '', test);
alert('Pool length:' + XMLHttp._objPool.length);
</script>
demo 下载xmlhttp.js
通过本JS脚本，我也做一个例子。
1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
2 <html xmlns="http://www.w3.org/1999/xhtml" >
3 <head>
4 <title>test</title>
5 <script type="text/javascript" src="connectpool.js"></script>
6 <script type="text/javascript">
7 function sendAJAX()
8 {
9 XMLHttp.sendReq('POST','receive.aspx', null, test);
10 }
11 function test(obj)
12 {
13 document.getElementById('nameList').innerHTML =obj.responseText;
14 }
15 setInterval('sendAJAX()',1000);
16 </script>
17 </head>
18 <body>
19 <div id="nameList"></div>
20 </body>
21 </html>
22
2 <html xmlns="http://www.w3.org/1999/xhtml" >
3 <head>
4 <title>test</title>
5 <script type="text/javascript" src="connectpool.js"></script>
6 <script type="text/javascript">
7 function sendAJAX()
8 {
9 XMLHttp.sendReq('POST','receive.aspx', null, test);
10 }
11 function test(obj)
12 {
13 document.getElementById('nameList').innerHTML =obj.responseText;
14 }
15 setInterval('sendAJAX()',1000);
16 </script>
17 </head>
18 <body>
19 <div id="nameList"></div>
20 </body>
21 </html>
22
1 <%@ Page Language="C#" %>
2 <%@ Import Namespace="System.Diagnostics" %>
3
4 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
5
6 <script runat="server">
7
8 protected void Page_Load(object sender, EventArgs e)
9 {
10 PerformanceCounter myMemory = new PerformanceCounter();
11 myMemory.CategoryName = "Memory";
12 myMemory.CounterName = "Available KBytes";
13
14 string txtResult = "-->当前可用内存：" + myMemory.NextValue().ToString() + "KB";
15 Response.Write(DateTime.Now.ToLongTimeString() + txtResult);
16 }
17 </script>
18
19 <html xmlns="http://www.w3.org/1999/xhtml" >
20 <head runat="server">
21 <title>Receive</title>
22 </head>
23 <body>
24 <form id="form1" runat="server">
25 <div>
26
27 </div>
28 </form>
29 </body>
30 </html>
31
2 <%@ Import Namespace="System.Diagnostics" %>
3
4 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
5
6 <script runat="server">
7
8 protected void Page_Load(object sender, EventArgs e)
9 {
10 PerformanceCounter myMemory = new PerformanceCounter();
11 myMemory.CategoryName = "Memory";
12 myMemory.CounterName = "Available KBytes";
13
14 string txtResult = "-->当前可用内存：" + myMemory.NextValue().ToString() + "KB";
15 Response.Write(DateTime.Now.ToLongTimeString() + txtResult);
16 }
17 </script>
18
19 <html xmlns="http://www.w3.org/1999/xhtml" >
20 <head runat="server">
21 <title>Receive</title>
22 </head>
23 <body>
24 <form id="form1" runat="server">
25 <div>
26
27 </div>
28 </form>
29 </body>
30 </html>
31
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