XMLHttpRequest instantiation indentify browser

function FactoryXMLHttpRequest()
{
if(window.XMLHttpRequest)
{
return new XMLHttpRequest(); //most likely includes all browsers except Microsoft IE
}
else if(window.ActiveXObject)
{
var msxmls = new Array
( 'Msxml2.XMLHTTP.5.0',
'Msxml2.XMLHTTP.4.0',
'Msxml2.XMLHTTP.3.0',
'Msxml2.XMLHTTP',
'Microsoft.XMLHTTP'
);

for (var i = 0; i < msxmls.length; i++)
{
try {
return new ActiveXObject(msxmls[i]);
}
catch (e)
{
}
}
}

throw new Error("Could not instantiate XMLHttpRequest");

}