Novices Performing Miracles

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    1.14.1 • Public • Published

    Build Status npm License: MIT


    This package aims to provide a way to:

    • Embed Lua to any Node.js, Deno or Web Application.
    • Run lua code in any operational system
    • Interop Lua and JS without memory leaks (including the DOM)

    API Usage

    To initialize, create a new Lua state, register the standard library, set a global variable, execute a code and get a global variable:

    const { LuaFactory } = require('wasmoon')
    // Initialize a new lua environment factory
    // You can pass the wasm location as the first argument, useful if you are using wasmoon on a web environment and want to host the file by yourself
    const factory = new LuaFactory()
    // Create a standalone lua environment from the factory
    const lua = await factory.createEngine()
    try {
        // Set a JS function to be a global lua function'sum', (x, y) => x + y)
        // Run a lua string
        await lua.doString(`
        print(sum(10, 10))
        function multiply(x, y)
            return x * y
        // Get a global lua function as a JS function
        const multiply ='multiply')
        console.log(multiply(10, 10))
    } finally {
        // Close the lua environment, so it can be freed

    CLI Usage

    Although Wasmoon has been designed to be embedded, you can run it on command line as well, but, if you want something more robust on this, we recommend to take a look at demoon.

    $: wasmoon [options] [file] [args]

    Available options are:

    • -l: Include a file or directory
    • -i: Enter interactive mode after running the files


    $: wasmoon -i sum.lua 10 30

    And if you are in Unix, you can also use it as a script interpreter with Shebang:

    #!/usr/bin/env wasmoon
    return arg[1] + arg[2]
    $: ./sum.lua 10 30

    When to use wasmoon and fengari

    Wasmoon compiles the official Lua code to webassembly and creates an abstraction layer to interop between Lua and JS, instead of fengari, that is an entire Lua VM rewritten in JS.


    Because of wasm, wasmoon will run Lua code much faster than fengari, but if you are going to interop a lot between JS and Lua, this may be not be true anymore, you probably should test on you specific use case to take the prove.

    This is the results running a heap sort code in a list of 2k numbers 10x(less is better):

    wasmoon fengari
    15.267ms 389.923ms


    Fengari is smaller than wasmoon, which can improve the user experience if in web environments:

    wasmoon fengari
    plain 393kB 214kB
    gzipped 130kB 69kB

    Fixing common errors on web environment

    Bundle/require errors can happen because wasmoon tries to safely import some node modules even in a browser environment, the bundler is not prepared to that since it tries to statically resolve everything on build time. Polyfilling these modules is not the right solution because they are not actually being used, you just have to ignore them:


    Add the resolve.fallback snippet to your config:

    module.exports = {
        entry: './src/index.js', // Here is your entry file
        resolve: {
            fallback: {
                path: false,
                fs: false,
                child_process: false,
                crypto: false,
                url: false,


    With the package rollup-plugin-ignore, add this snippet to your config:

    export default {
        input: 'src/index.js', // Here is your entry file,
        plugins: [ignore(['path', 'fs', 'child_process', 'crypto', 'url'])],


    Add the section browser on package.json:

        "main": "src/index.js",
        "browser": {
            "child_process": false,
            "fs": false,
            "path": false,
            "crypto": false,
            "url": false

    How to build

    Firstly download the lua submodule and install the other Node.JS dependencies:

    git submodule update --init # download lua submodule
    npm i # install dependencies

    Windows / Linux (Docker way)

    You need to install docker and ensure it is on your PATH.

    After cloned the repo, to build you just have to run these:

    npm run build:wasm:docker:dev # build lua
    npm run build # build the js code/bridge
    npm test # ensure everything it's working fine

    Ubuntu / Debian

    You need to install emscripten and ensure it is on your PATH.

    After cloned the repo, to build you just have to run these:

    npm run build:wasm:dev # build lua
    npm run build # build the js code/bridge
    npm test # ensure everything it's working fine


    npm i wasmoon

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    • ceifa