Fengari is a lua VM written in Javascript. It's implementation makes use of the JS garbage collector, which means it is fully capable of cross language interop.

• Call any JS function from Lua
• Give Lua tables/functions/userdata to Javascript

js = require "js"

A userdata representing JavaScript null

A reference to the JavaScript global context. In the browser, this is usually equivalent to the window object. In node.js it's equal to global.

Invokes the JavaScript new operator on constructor passing the arguments specified.

Returns the created object.

Returns a iterating function and an iterator state that behave like a JavaScript for...of loop. Suitable for use as a lua iterator. e.g.

for f in js.of(js.global:Array(10,20,30)) do
	print(f)
end

Creates a JavaScript Proxy object. The proxy supports calling (apply), indexing (get and has) and setting (set and deleteProperty).

type is the desired result for typeof proxy; it may be "function" (the default) or "object".

Note that JavaScript coerces all types except Symbols to strings before using them as a key in an indexing operation.

Coerces the value x to a number using JavaScript coercion rules.

Returns if the value x is an instance of the class y via use of the JavaScript instanceof operator

The __pairs Symbol can be used to describe how to iterate over a JavaScript object. Use Symbol.for("__pairs") to get the symbol. It should be used as a key on your objects, where the value is a function returning an object with three properties: "iter", "state" and "first".

"iter" should be a function that follows the standard Lua generic for protocol, that is, it gets called with your state (as this) and the previous value produced; it should return an array of values or undefined if done.

e.g. to make pairs on a Map return entries in the map via the iterator symbol

Map.prototype[Symbol.for("__pairs")] = function() {
	return {
		iter: function(last) {
			var v = this.next();
			if (v.done) return;
			return v.value;
		},
		state: this[Symbol.iterator]()
	};
}

A default __pairs is attached to Object.prototype that uses Object.keys.