XML document onreadystatechange is not being fired.

I have a piece of javascript(using .htc file) code that is working fine in IE9. To let work in IE 11 or latest version i had to convert .htc file to javascript file so that i did. but some of code is not working like XmlDocument onreadystatechange event is not being fired in converted document.
Here is my code.

var oXml = document.createElement("XML");
document.body.appendChild(oXml);
oS = new Object();
oS.sXmlHttp = null;
oS.aXmlHttp = null;
oS.fPending = true;
oS.nextCall = null;
oS.lastCall = null;
oS.url = url;
oS._oXml = oXml;
oS.ns = new Array();
oS.nsalias = new Array();
if (options != null) {
  oS.fSeq = options.reuseConnection;
  oS.SOAPHeader = options.SOAPHeader;
}
if (oS.fSeq == null)
    oS.fSeq = false;
_sdl[url] = oS;
oXml.service = userName;
oXml.onreadystatechange = getWsdl;
oXml.src = url;
oXml = xmlDoc;