locationJS.dart

@JS('navigator.geolocation') // navigator.geolocation namespace
library jslocation; // library name can be whatever you want

import "package:js/js.dart";
// locjs.getCurrentPosition(allowInterop((pos) => success(pos))

@JS('getCurrentPosition') // Accessing method getCurrentPosition from Geolocation API
external void getCurrentPosition(Function success(GeolocationPosition pos), Function error(var err), options);

@JS('watchPosition') // Accessing method watchPosition from Geolocation API
external void watchPosition(Function success(GeolocationPosition pos), Function error(var err), options);

@JS()
@anonymous
class GeolocationCoordinates {
  external double get latitude;
  external double get longitude;
  external double get altitude;
  external double get accuracy;
  external double get altitudeAccuracy;
  external double get heading;
  external double get speed;

  external factory GeolocationCoordinates(
      {double latitude,
      double longitude,
      double altitude,
      double accuracy,
      double altitudeAccuracy,
      double heading,
      double speed});
}

@JS()
@anonymous
class GeolocationPosition {
  external GeolocationCoordinates get coords;
  external factory GeolocationPosition({GeolocationCoordinates coords});
}

@JS()
@anonymous
class GeolocationPositionError {
  external int get code;
  external String get message;
  external factory GeolocationPositionError({int code, String message});
}

@JS()
external mapOptions(Options options);

@JS()
@anonymous
class Options {
  external bool get enableHighAccuracy;
  external double get timeout;
  external double get maximumage;

  // Must have an unnamed factory constructor with named arguments.
  external factory Options({bool enableHighAccuracy, double timeout, double maximumage});
}