Обещания

W3C Geo и JavaScript promise:

var getPosition = function (options) {
  return new Promise(function (resolve, reject) {
    navigator.geolocation.getCurrentPosition(resolve, reject, options);
  });
}

getPosition()
  .then((position) => {
    console.log(position);
  })
  .catch((err) => {
    console.error(err.message);
  });

Отсюда