Code snippet of tutorial running tracker

tracker.js

const refreshMeter = (detail) => {
  return new Promise((resolve) => {

    if (path == null) return resolve(detail);

    if (!isStart) return resolve(detail);

    const delta = calculateDelta(path._latlngs)
    accumulatedDistance += delta;

    const formattedDistance = (round(accumulatedDistance, 3)).toLocaleString('en-US', { minimumFractionDigits: 3 })
    distanceBox.textContent = formattedDistance;
    report(`3. Updated path with ${delta} km | accumulatedDistance = ${formattedDistance}`);

    return resolve(detail);
  })
}