グーグルで少し検索すると、基本的な問題に対する良い答えが得られます
/*
Provide the XMLHttpRequest constructor for Internet Explorer 5.x-6.x:
Other browsers (including Internet Explorer 7.x-9.x) do not redefine
XMLHttpRequest if it already exists.
This example is based on findings at:
http://blogs.msdn.com/xmlteam/archive/2006/10/23/using-the-right-version-of-msxml-in-internet-explorer.aspx
*/
if (typeof XMLHttpRequest === "undefined") {
XMLHttpRequest = function () {
try { return new ActiveXObject("Msxml2.XMLHTTP.6.0"); }
catch (e) {}
try { return new ActiveXObject("Msxml2.XMLHTTP.3.0"); }
catch (e) {}
try { return new ActiveXObject("Microsoft.XMLHTTP"); }
catch (e) {}
// Microsoft.XMLHTTP points to Msxml2.XMLHTTP and is redundant
throw new Error("This browser does not support XMLHttpRequest.");
};
}
また
/**
* Gets an XMLHttpRequest. For Internet Explorer 6, attempts to use MSXML 6.0,
* then falls back to MXSML 3.0.
* Returns null if the object could not be created.
* @return {XMLHttpRequest or equivalent ActiveXObject}
*/
function getXHR() {
if (window.XMLHttpRequest) {
// Chrome, Firefox, IE7+, Opera, Safari
return new XMLHttpRequest();
}
// IE6
try {
// The latest stable version. It has the best security, performance,
// reliability, and W3C conformance. Ships with Vista, and available
// with other OS's via downloads and updates.
return new ActiveXObject('MSXML2.XMLHTTP.6.0');
} catch (e) {
try {
// The fallback.
return new ActiveXObject('MSXML2.XMLHTTP.3.0');
} catch (e) {
alert('This browser is not AJAX enabled.');
return null;
}
}
}
参照 : http://en.wikipedia.org/wiki/XMLHttpRequestおよびhttp://www.webmasterworld.com/javascript/4027629.htm