lua-in-browser

How to use Lua in browser with wasmoon

Quick way (using my pre-built wasmoon_min.js)

TL;DR: Clone the repo, put your lua code in init function inside html/main.html and you are good to go. All test* files and folders are for demonstration purproses only and can be removed.

Minimal version of wasmoon.js is built from the following code:

const {LuaFactory} = require('wasmoon')
const factory = new LuaFactory()
export {factory}

It loads factory into a global variable lb.

Having wasmoon.js loaded as a script in HTML, you then need to create Lua engine

const factory = await lb.factory
const lua = await factory.createEngine()

and you can run Lua using doString method:

 await lua.doString('return ("hello from lua")')

lua.global.get and lua.global.set allow two-way binding of values and functions between Lua and JS:

>>> await lua.doString(`function sum(x,y) return x+y end`)
>>> sum = lua.global.get("sum")
>>> sum(1,5) 
6

>>> function multiply(x,y) {return x*y}
>>> lua.global.set('multiply', multiply)
>>> await lua.doString(`return multiply(2,8)`)
16

To use an external file, you need to mount it:

factory.mountFile(path, content)

Using fetch, we can transform it into an AJAX request:

lua.global.set('fetch', (url) => fetch(url));

async function mountFile(file_path, lua_path) {
    const fileContent = await fetch(file_path).then(data => data.text())
    await factory.mountFile(lua_path, fileContent)
}

Now we can require files from our server:

await mountFile('../any/long/path/to/file.lua', 'test.lua')
await lua.doString('require("test")')

So as to not needing to mount all the modules in advance we can replace the default require function (note fetch that we set earlier):

function require(path)
  print('required '..path,'from:', debug.getinfo(2).name)
  local resp = fetch(string.format('/lua/%s.lua',path)):await()
  local text = resp:text():await()
  local module = load(text)()
  print('loaded '..path)
  return module
end

An extended version of this function is located inside html\main.html. It is cached (with memoize) and can handle dot-separated package paths, e.g. require ("package.subpackage.module")

---

Build your own wasmoon.js with webpack

1. Install node
2. cd build
3. npm install wasmoon
4. Set up paths in webpack.config.js
5. npx webpack

Now you should have your wasmoon.js in the output folder