Looks fascinating!
Well NIF’s and Ports sound like great integration points between Rayscript and javascript at least. ^.^
If you are curious in Elixir AST → Javascript compilation, there is an old project that did most of it at GitHub - synrc/shen: 🐉 SHEN: Erlang JavaScript Compiler · GitHub if you are curious about any code to swipe or so since that project is long-dead. 
Shen worked based on a parse_transform though, much different method.
