LuaJS

Lua VM running in Javascript (using emscripten)

Setup Instructions

Make certain to download your git submodules, run git submodule update --init --recursive.

You'll need emscripten and NodeJS installed. If you're running a system that supports homebrew, you can brew install:

Installing Homebrew
Install Emscripten: brew install emscripten && brew install node

Build instructions

Run npm install && npm run clean && npm run build then you have the compiled files in the dist folder.

Usage of Lua from JavaScript

LuaJS.newState().then(async (L) => {
    let value;
    value = await L.run("return 1+2"); //value == [3]

    value = await L.run("return {a = 1, b = 2}"); //value[0] instanceof Module.Table, value[0] instanceof Module.Reference
    value[0].get("a"); // == 1
    console.log(value);
    console.log(value[0].toObject(true, true)); //converts Module.Table to JavaScript object (will drop all other Module.Reference-s if unrefAll == true)
    value[0].unref();

    let func = await L.run("return function(a,b) return a + b end"); //func[0] instanceof Module.Function, func[0] instanceof Module.Reference
    value = func[0].call(3,4); //value == [7]
    console.log(value);
    func[0].unref();
});

Using .unref() is optional as LuaJS does utilize Finalizers. However, those can be called at any time, so if you are memory constrained, manual unref might help!

Usage of JavaScript from Lua

Lua knows the library js, where the js.global table equals the JavaScript window object

When you call JS functions from Lua, the function parameters will always be automatically converted to JS equivalents (and internally .unref()'d, except functions).

You can convert JS objects/arrays to native Lua tables by using jsObject:toTable(recursive), however you can also directly index JS objects from Lua.

Warning: You need to call all JS functions either like js.global:alert("testmessage") or local alert = js.global.alert; alert(nil, "testmessage"). The first argument will be used as the "this" context in JavaScript.

Using Lua inline in HTML

If you call enableLuaScriptTags(document), you can specify <script type="text/lua"> tags just like JavaScript tags with either inline scripts or a src attribute.

Below is an example HTML document that enables Lua scripts for the entire page:

<!DOCTYPE html>
<html>
    <head>
        <script type="module" src="./dist/luajs.mjs"></script>
        <script type="module">
            import emscriptenInit from './dist/luajs.mjs';
            const LuaJS = await emscriptenInit();

            LuaJS.newState().then(async (L) => {
                await L.enableLuaScriptTags(document);
            });
        </script>
        <script type="text/lua">
            js.global.console:log("Hello world")
        </script>
    </head>
</html>

Using Lua in NodeJS

The compiled module can be used in NodeJS as follows:

// EITHER: Import (ES6 modules, .mjs/.mts)
import { LuaJS } from '@doridian/luaj';
// OR: require (CommonJS, .cjs/.cts)
const { LuaJS } = require('@doridian/luajs');

LuaJS.newState().then(async (L) => {
    console.log(await L.run("return 42 + 69"));
});

Doridian / LuaJS