You can just take the original Lua interpreter source code and compile that to asm.js or WebAssembly without changes. Loading dependencies from the web requires an asynchronous reimplementation of the "require" command though, but it's all quite trivial. The result is about 100 to 150 KByte compressed. The only downside (beside the added size) is that the Lua code is still running interpreted, not JITed. That's why I think that a combination of WebAssembly for performance critical code, and Typescript (compiled to Javascript) for the 'scripting part' makes more sense than WebAssembly+Lua, since this doesn't have those downside (no additional size overhead for the interpreter, and the JS will be JITed).