Fengari‑Interop is a JavaScript library that bridges Lua code running on Fengari (a Lua VM implemented in JavaScript) with the surrounding JavaScript environment. It lets Lua scripts call any JS function, create objects, iterate over JS collections, and pass Lua tables, functions, or userdata back to JavaScript, while providing a small Lua “js” module and a complementary JS API for converting values. The project is aimed at developers who want to embed or extend Lua scripts inside web browsers or Node.js applications and need seamless two‑way inter‑operation between the two languages.