Create a jsajax request class by yourself

// Use literal syntax to define an object: XMLHttpvarXMLHttp {// define the first attribute, which is used to cache the XMLHttpRequest object array XMLHttpRequestPool: [], // The first method of the object, this method is used to return an XMLHttpRequest object... synta // use literal syntax to define an object: XMLHttp
Var XMLHttp =
{
// Define the first attribute, which is used to cache the array of the XMLHttpRequest object
XMLHttpRequestPool: [],
// The first method of the object. This method is used to return an XMLHttpRequest object.
GetInstance: function ()
{
// Retrieve an idle XMLHttpRequest from the XMLHttpRequest object pool
For (var I = 0; I <this. XMLHttpRequestPool. length; I ++)
{
// If the readyState of XMLHttpReuqest is 0 or 4,
// Both indicate that the current XMLHttpRequest object is an idle object.
If (this. XMLHttpRequestPool [I]. readyState = 0 |
This. XMLHttpRequestPool [I]. readyState = 4)
{
Return this. XMLHttpRequestPool [I];
}
}
// If there is no idle space, a new XMLHttpRequest object will be created again.
This. XMLHttpRequestPool [this. XMLHttpRequestPool. length]
= This. createXMLHttpRequest ();
// Return the created XMLHttpRequest object
Return this. XMLHttpRequestPool [this. XMLHttpRequestPool. length-1];
},
// Create a new XMLHttpRequest object
CreateXMLHttpRequest: function ()
{
// For the DOM 2 standard browser
If (window. XMLHttpRequest)
{
Var objXMLHttp = new XMLHttpRequest ();
}
// For Internet Explorer
Else
{
// Set all XMLHTTP ActiveX Control built in Internet Explorer to an array
Var MSXML = ['msxml2. XMLHTTP.5.0 ', 'msxml2. XMLHTTP.4.0 ',
'Msxml2. XMLHTTP.3.0 ', 'msxml2. xmlhttp', 'Microsoft. xmlhttp'];
// Initialize the XMLHTTP control built in Internet Explorer in sequence and try to create the XMLHttpRequest object
For (var n = 0; n <MSXML. length; n ++)
{
Try
{
// If the XMLHttpRequest object can be created normally, use break to exit the loop
Var objXMLHttp = new ActiveXObject (MSXML [n]);
Break;
}
Catch (e)
{
}
}
}
// Some Mozilla versions do not have the readyState attribute
If (objXMLHttp. readyState = null)
{
// Directly set its readyState to 0
ObjXMLHttp. readyState = 0;
// For Browsers without the readyState attribute, associate the load action with the following function.
ObjXMLHttp. addEventListener ("load", function ()
{
// After loading data from the server, set the readyState status to 4.
ObjXMLHttp. readyState = 4;
If (typeof objXMLHttp. onreadystatechange = "function ")
{
ObjXMLHttp. onreadystatechange ();
}
}, False );
}
Return objXMLHttp;
},
// Define the third method of the object: send the request (method [POST, GET], address, Data, callback function)
SendRequest: function (method, url, data, callback)
{
Var objXMLHttp = this. getInstance ();
With (objXMLHttp)
{
Try
{
// Add an additional randnum request parameter to prevent response from the IE Cache Server
If (url. indexOf ("? ")> 0)
{
Url + = "& randnum =" + Math. random ();
}
Else
{
Url + = "? Randnum = "+ Math. random ();
}
// Open the connection to the server
Open (method, url, true );
// For post requests
If (method = "POST ")
{
// Set the Request Header
SetRequestHeader ('content-type ',
'Application/x-www-form-urlencoded ');
Send (data );
}
// For GET requests
If (method = "GET ")
{
Send (null );
}
// Set the callback function for status change
Onreadystatechange = function ()
{
// When the server completes, and receives a normal Server Response
If (objXMLHttp. readyState = 4 &&
(ObjXMLHttp. status = 200 |
ObjXMLHttp. status = 304 ))
{
// Call the callback function to handle the response when the response time is ripe.
Callback (objXMLHttp );
}
}
}
Catch (e)
{
Alert (e );
}
}
}
};

From Hurry's column