README.md

Use this with two Mapbox GL JS map instances as arguments to the syncMaps function and it'll keep them pointed at the same thing.

mapbox_gl_sync.js

function copyPosition(a, b) {
  b.jumpTo({
    center: a.getCenter(),
    zoom: a.getZoom(),
    bearing: a.getBearing(),
    pitch: a.getPitch()
  });
}

function syncMaps(a, b) {
  a.on('moveend', function() {
    copyPosition(a, b);
  });
  b.on('moveend', function() {
    copyPosition(b, a);
  });
}