A lightweight scripting language written in Dart for embedding in Flutter apps.

简体中文页面

Hetu is a lightweight scripting language purely written in Dart for embedding in Flutter apps. Our goal is to enable Flutter app & game to have hotfix and scripting ability.

Documentation 中文文档

• Modern programming language syntax likes typescript/kotlin/swift, need very little time to get familiar with.
• Full scripting language abilities: class OOP, prototype OOP, FP, module, errors, etc.
• JavaScript-friendly APIs: use familiar names like push, filter, padStart, Math.PI, Promise.resolve and console.warn, as aliases of the Dart-backed implementations.
• Runs on all platforms that flutter supports, including web browsers and desktop.
• Extremely easy on binding, call Dart functions in script or call script functions in Dart with just one line.

Test Hetu script in the online playground.

To eval a string literal of Hetu code in Dart.

import 'package:hetu_script/hetu_script.dart';

void main() {
  final hetu = Hetu();
  hetu.init();
  hetu.eval(r'''
    var ht = {
      name: 'Hetu',
      greeting: () {
        print('Greetings from ${this.name}!')
      }
    }
    ht.greeting()
  ''');
}

To pass a Map to script, modify it in script and get it back:

import 'package:hetu_script/hetu_script.dart';

void main() {
  final hetu = Hetu();
  hetu.init(externalFunctions: {
    'hello': () => {'greetings': 'greetings from Dart!'},
  });
  var hetuValue = hetu.eval(r'''
      external function hello
      var dartValue = hello()
      dartValue['reply'] = 'Hi, this is Hetu.'
      dartValue // the script will return the value of it's last expression
      ''');

  print('hetu value: $hetuValue');
}

You can check the documentation for more information on the grammar and binding.

If you come from JavaScript or TypeScript, many standard library APIs can be used with the names you already know. These are aliases of the Dart-backed implementations, so script values stay fully interoperable with the Dart host:

var list = [1, 2, 3]
list.push(4)
var evens = list.filter((n) => n % 2 == 0).toList()

var text = '7'.padStart(3, '0') // '007'
var max = Math.max(3, 1, 4, 1, 5) // 5

Promise.resolve(42).then((value) => print(value))
console.warn('done')

Note that the behavior always follows the Dart SDK (for example, filter returns a lazy Iterable). Check the JavaScript developers guide for the full alias table and the differences to watch out for.

The hetu_script_dev_tools package includes an automatic binding generator for Dart classes, enums, and function typedefs marked with @HTBinding(). It generates both Dart-side HTExternalClass bindings and Hetu-side external class declarations.

You can use it with build_runner:

dart pub add --dev hetu_script_dev_tools build_runner
dart run build_runner build

Or generate bindings directly with the CLI:

hetu bind -u lib/src -o gen/dart -s gen/ht

See the binding guide for details.

If you are using VS Code, you can download this extension to get basic highlight and dart snippets on bindings.

We have a command line REPL tool for quick testing. You can install it globally with dart install:

dart install https://github.com/hetu-script/hetu-script.git --git-path packages/hetu_script_dev_tools

Or install from a local path:

dart install --source path /path/to/hetu-script/packages/hetu_script_dev_tools

Then you can use command line tool 'hetu' in any directory on your computer.

More information about the command line tool can be found by enter 'hetu -h'.

If no arguments is provided, enter REPL mode.

In REPL mode, every exrepssion you entered will be evaluated and print out immediately.

If you want to write multiple line in REPL mode, use '\' to end a line.

>>>var a = 42
null // repl print
>>>a
42 // repl print
>>>function meaning {\
return a }
null // repl print
>>>meaning
meaning() -> any // repl print
>>>hello()
42 // repl print

You can check this official document for more information on 'dart install'.

You can support my project by simply giving it a star on GitHub.

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