twogeojson
It's like togeojson except much faster, newer, and doesn't work in browsers because it uses a streaming parser - htmlparser2.
install
npm install twogeojson
example
var tj = require('twogeojson');
var gpxParser = tj.gpx();
gpxParser.write('gpxstringofdata');
gpxParser.end();
var geoJson = gpxParser.data();