flutter调用JavaScript

flutter_js: ^0.0.2+1

import 'package:flutter/material.dart';
import 'dart:async';

import 'package:flutter/services.dart';
import 'package:flutter_js/flutter_js.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  String _jsResult = '';
  int _idJsEngine = -1;
  @override
  void initState() {
    super.initState();
    initJsEngine();
  }

  // Platform messages are asynchronous, so we initialize in an async method.
  Future<void> initJsEngine() async {
  

    try {
      _idJsEngine = await FlutterJs.initEngine();
    } on PlatformException catch (e) {
      print('Failed to init js engine: ${e.details}');
    }

    // If the widget was removed from the tree while the asynchronous platform
    // message was in flight, we want to discard the reply rather than calling
    // setState to update our non-existent appearance.
    if (!mounted) return;


  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('FlutterJS Example'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text('JS Evaluate Result: $_jsResult\n'),
              SizedBox(height: 20,),
              Padding(padding: EdgeInsets.all(10), child: Text('Click on the big JS Yellow Button to evaluate the expression bellow using the flutter_js plugin'),),
              Padding(
                padding: const EdgeInsets.all(8.0),
                child: Text("Math.trunc(Math.random() * 100).toString();", style: TextStyle(fontSize: 12, fontStyle: FontStyle.italic, fontWeight: FontWeight.bold),),
              )
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          backgroundColor: Colors.transparent, 
          child: Image.asset('assets/js.ico'),
          onPressed: () async {
            try {
              String result = await FlutterJs.evaluate(
                  "Math.trunc(Math.random() * 100).toString();", _idJsEngine);
              setState(() {
                _jsResult = result;
              });
            } on PlatformException catch (e) {
              print('ERRO: ${e.details}');
            }
          },
        ),
      ),
    );
  }
}

Alternatives 

There were another packages which provides alternatives to evaluate javascript in flutter projects:

https://pub.flutter-io.cn/packages/flutter_liquidcore 

Good, is based on https://github.com/LiquidPlayer/LiquidCore

It is based on V8 engine so the exectuable library is huge (20Mb). So the final app will be huge too.

https://pub.flutter-io.cn/packages/interactive_webview 

Allows to evaluate javascript in a hidden webview. Does not add weight to size of the app, but a webview means a entire browser is in memory just to evaluate javascript code. So we think an embeddable engine is a way better solution.

https://pub.flutter-io.cn/packages/jsengine 

Based on jerryscript which is slower than quickjs. The jsengine package does not have implementation to iOS.