Basic mapbox-gl animation loop necessary for smoothly animating GeoJSON sources.

mapbox-animation.js

const source = this.map.getSource('my-source');

function loop() {
  source.on('data', requestFrame);
  source.setData(updatedGeoJson);
}

function requestFrame(event) {
  if (event.dataType !== 'source') {
    return;
  }

  source.off('data', this.requestFrame);
  requestAnimationFrame(loop);
}