JavaScript differences between IE 11 and Edge?

Using Design Studio, the following JavaScript was added to AP20.1 to retrieve the Requester for a PO.  When run in IE 11 (in default Edge emulation mode) on Windows 7, it runs successfully - the count shows that 1 record was retrieved and the vRequester variable is set to the Requester from the database.  When run in Edge on Windows 10, the count also shows that 1 record was retrieved, but vRequester is always blank.

     var strPDL = portalWnd.oUserProfile.getAttribute("productline");
     var s = https://server + portalWnd.DMEPath;
     s += "?PROD="+strPDL;
     s += "&FILE=POLINESRC";
     s += "&INDEX=PLSSET1";
     s += "&KEY=" + parseInt(CoNbr,10);
     s += "= =";
     s += escape(PONbr);
     s += "&FIELD=REQUESTER";
     s += "&OUT=XML&DELIM=~";
     var sReturn=portalWnd.httpRequest(s);
     var vObjDMEXML = new portalWnd.DataStorage(sReturn);
     var vRecords = vObjDMEXML.document.getElementsByTagName("RECORD");
     var count = vObjDMEXML.document.getElementsByTagName("RECORDS")[0].getAttribute("count");    
     if (count > 0) var vCols = vRecords[0].getElementsByTagName("COL");
     var vRequester = vCols[0].firstChild.data;  

I was told that I should use firstElementChild. instead of .firstChild.  However, I'm struggling to get firstElementChild to work.  Does anyone have an example of use of firstElementChild to extract returned data from a DME call? 

Thank you