createGPX.js

const fs = require('fs-extra');
const path = require('path');
const readline = require('readline');

async function createGPX(options) {
    await writeHeader(options);
    const fileStream = fs.createReadStream(options.input);

    const rl = readline.createInterface({
        input: fileStream,
        crlfDelay: Infinity
    });

    for await (const line of rl) {
      if (line){        
        const point = JSON.parse(line);
        let trkpt = '			<trkpt ';
        trkpt += `lat="${point.lat}" lon="${point.lon}">\n`;
        trkpt += `				<time>${point.t}</time>\n`;
        trkpt += '			</trkpt>\n';
        fs.appendFileSync(path.join(options.outputDir, 'track.gpx'), trkpt);
      }
    }
    await writeFooter(options);
    return [path.join(options.outputDir, 'track.gpx')];
}

async function writeHeader(options) {
  const header = `<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
  <gpx version="1.1" creator="${options.creator}"
          xmlns="http://www.topografix.com/GPX/1/1"  
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
          xmlns:gpxx="http://www8.garmin.com/xmlschemas/GpxExtensions/v3"
          xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd https://www8.garmin.com/xmlschemas/GpxExtensions/v3 https://www8.garmin.com/xmlschemas/GpxExtensions/v3/GpxExtensionsv3.xsd"
  >
      <metadata/>
      <trk>
          <trkseg>
  `;
  fs.writeFileSync(path.join(options.outputDir, 'track.gpx'), header);
}

async function writeFooter(options) {
  const footer = '		</trkseg>\n	</trk>\n</gpx>';
  fs.appendFileSync(path.join(options.outputDir, 'track.gpx'), footer);
}

module.exports = createGPX;