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; } xhr.open( method, url, async );