I guess it would depend on the JS engine. If the player is the one writing JS, and you want a scaled down environment (since it's not an app in the browser), probably making your own JS parser/engine could be the way to go? You'd want the JS engine to be inside the game engine somehow.
This is definitely a requirement, a very scaled down one since I don't want any interaction with the outside world apart from the game engine (for determinism purposes).
> probably making your own JS parser/engine could be the way to go
That sounds like a lot of work to do well. If I had infinite time I suppose re-implementing a common language would be the best way forwards, but I don't, especially for a hobby project.
Yeah I can't comment much on how long a JS engine would take. You could start using V8 I guess, but I would think using an existing JS engine inside a game engine might by tricky because they seem complex. JS the language is easy to create a parser for, and that might be what you really want to be custom in order to do other things in between the JS code. Maybe try looking for stripped down JS engines that have source code to see how hard it is. I'm also assuming you will code this game with C++ for performance, but maybe a JS/HTML game could leverage V8 from the browser, if that was your initial thinking.
I'd be delighted to use V8... if I could figure out a way to get a deterministic estimate of the runtime of scripts (e.g. in languages that compile to a bytecode I could add a "bytecodes executed counter" easily enough).
I'm coding the game in Rust, but I really don't care what the language is coded in, linking in a language runtime isn't a problem.
