h3_web_plus 1.0.0+v4.2.1

Dart JS interop implementation of the abstract H3 interface from h3_common_plus. Not intended for direct use.

h3_web_plus

h3_web_plus provides a low-level web implementation of H3 bindings via JavaScript interop (JS FFI) using the h3-js library.

⚠️ This package is not intended for direct use. Instead, use one of the higher-level packages:

• h3_dart_plus — For general Dart apps.
• h3_flutter_plus — For Flutter apps on Android, desktop, and web.

History & Migration

h3_web_plus is part of a complete rework of the Dart and Flutter bindings for Uber's H3 library, modernizing the unmaintained h3_web by festelo, which was based on H3 v3.7.2.

The migration includes:

• Full update to H3 v4.2.1, supporting all stable functions.
• Inclusion of vertex mode and experimental APIs.
• A restructured ecosystem with a clear separation of platform-specific implementations.

See the Changelog for detailed update notes and migration guidance.

⚠️ Web Null Safety Warning

Due to limitations in the JS FFI tooling, any value returned from h3_web_plus should be treated as nullable, even if Dart’s analyzer marks it as non-nullable.

This affects all consumers of the web implementation. If you’re using h3_dart_plus or h3_flutter_plus on the web, the issue is contained internally—but you may still want to verify that outputs are not null before using them in production code.

Examples of safe casting:

final result = h3_js.h3ToCenterChild(index, res) as String?;
final list = h3_js.polyfill([...], 5).cast<String>();

Null safety will be improved in future updates once better tooling or custom bindings are introduced.

Setup

To use this package in a web environment, you must include the h3-js JavaScript library manually. Add the following line to your HTML file before your compiled Dart script (main.dart.js):

<script defer src="https://unpkg.com/h3-js@4.2.1"></script>

Example (Direct Use)

final h3 = const H3Web();
final hexagons = h3.polygonToCells(
  resolution: 6,
  coordinates: [
    LatLng(lat:37.775, lng:-122.418),
    LatLng(lat:37.776, lng:-122.419),
    LatLng(lat:37.777, lng:-122.417),
  ],
);

License

This project is licensed under the Apache 2.0 License.