new XMLHttpRequest();
}
else
{
try
{
xhr = new XMLHttpRequest("MSXML2.XmlHttp.5.0") || new XMLHttpRequest("MSXML2.XmlHttp.4.0") ||
new XMLHttpRequest("MSXML2.XmlHttp.3.0") || new XMLHttpRequest("MSXML2.XmlHttp.2.0") ||
new XMLHttpRequest("Microsoft.XmlHttp");
} catch ( e ) {}
}
// if xhr object does not supported or url not given, exit
xhr.onreadystatechange = function () {
if ( xhr.readyState != 4 ) return;
if ( xhr_done != null ) xhr_done = true;
callback ? callback( xhr ) : null;
}