flutter_qjs

A quickjs engine for flutter.

Feature

This plugin is a simple js engine for flutter using the quickjs project. Plugin currently supports Windows, Linux, and Android.

Each FlutterJs object creates a new thread that runs a simple js loop.

ES6 module with import function is supported and can manage in dart with setModuleHandler.

A global async function dart is presented to invoke dart function, and Promise is supported so that you can use await or then to get external result from dart. Data convertion between dart and js are implemented as follow:

dart	js
Bool	boolean
Int	number
Double	number
String	string
Uint8List/Int32List/Int64List	ArrayBuffer
Float64List	number[]
List	Array
Map	Object
Closure(List) => Future	function(....args)

notice:

1. All the Uint8List/Int32List/Int64List sent from dart will be converted to ArrayBuffer without marked the size of elements, and the ArrayBuffer will be converted to Uint8List.

2. function can only sent from js to dart and all the arguments will be packed in a dart List object.

Getting Started

1. Create a FlutterJs object. Make sure call destroy to terminate thread and release memory when you don't need it.

FlutterJs engine = FlutterJs();
// do something ...
await engine.destroy();
engine = null;

2. Call setMethodHandler to implements dart interaction. For example, you can use Dio to implements http in js:

await engine.setMethodHandler((String method, List arg) async {
  switch (method) {
    case "http":
      Response response = await Dio().get(arg[0]);
      return response.data;
    default:
      return JsMethodHandlerNotImplement();
  }
});

and in javascript, call dart function to get data:

dart("http", "http://example.com/");

3. Call setModuleHandler to resolve js module. For example, you can use assets files as module:

await engine.setModuleHandler((String module) async {
  return await rootBundle.loadString("js/" + module.replaceFirst(new RegExp(r".js$"), "") + ".js");
});

and in javascript, call import function to get module:

import("hello").then(({default: greet}) => greet("world"));

4. Use evaluate to run js script, and try-catch is needed to capture js exception.

try {
  print(await engine.evaluate(code ?? '', "<eval>"));
} catch (e) {
  print(e.toString());
}

This example contains a complete demonstration on how to use this plugin.