How to convert this c# linq-to-xml method into javascript

Question

I am converting legacy .NET server code into node.js server. Generally it's going OK but I am stuck with the code shown below. I have found a library for a JS LINQ equivalent (which may be OTT for my requirements), and a library for dealing with XML data, but finding equivalents for Descendants , Attribute etc is what's stopping me from progressing this.

Thanks in advance for any help.

        public static Track ParseGPX()
        {

            List<Position> Px = new List<Position>();
            IEnumerable<Track> tracks =
                    from trackElement in root.Descendants(ns1 + "trkseg")
                    select new Track
                    {
                        TrackPoints =
                            (from trackPointElement in trackElement.Descendants(ns1 + "trkpt")
                             select new TrackPoint
                             {
                                 pos = new Position
                                 {
                                     LatitudeDegrees = XmlConvert.ToDouble(trackPointElement.Attribute("lat").Value),
                                     LongitudeDegrees = XmlConvert.ToDouble(trackPointElement.Attribute("lon").Value),

                                 },
                                 AltitudeMeters = trackPointElement.Element(ns1 + "ele") != null
                                                 ? Convert.ToDouble(trackPointElement.Element(ns1 + "ele").Value) : 0.0,
                             }).ToList()
                    };

            return tracks.SingleOrDefault();
        }