What is it?

Fengari (Moon in greek) is the Lua VM written in JavaScript.
It uses JavaScript’s garbage collector so that interoperability with the DOM is non-leaky.

It comes with a simple module,
that renders any interaction with JavaScript and the DOM transparent:

local js=require "js"
local window=js.global

window:alert("Hello from Fengari!")

local js=require "js"
local window=js.global
local document=window.document

print("Document's title: " .. document.title)

Lua in the browser means you can use coroutines to write beautiful asynchronous code:

local js=require "js"
local window=js.global

local function sleep(delay)
    local co=assert(coroutine.running(), "Should be run in a coroutine")

    window:setTimeout(function()
        assert(coroutine.resume(co))
    end, delay*1000)

    coroutine.yield()
end

coroutine.wrap(function()
    print "Going to sleep now..."

    sleep(3)

    print "Sleep well?"
end)()

Test it out!

This REPL is itself written in Lua.

Getting started

The easiest way to get started with Fengari in the browser is to use fengari-web.
This module will watch the DOM for any and run them with Fengari.

1. Download fengari-web:

   $ curl -L -O https://github.com/fengari-lua/fengari-web/releases/download/v0.1.4/fengari-web.js

2. Include it in your webpage:

   script src="fengari-web.js" type="text/javascript">script>

3. Now any script of type application/lua will be run by fengari:

   script type="application/lua">
   print("hello world!")
   script>
   
   script src="/my-script.lua" type="application/lua" async>script>

Structure

Fengari is spread across several repositories:

• fengari: the core, largely a port of the PUC-Rio C implementation of Lua
• fengari-web: to use Fengari in the browser as easily as you might use JavaScript
• fengari-interop: a lua library that makes interoperating with JavaScript objects simple, it is already included in fengari-web
• fengari-node-cli: Lua CLI but running on top of Node.js
• fengari-loa