So, the experiment was quite a success!
My module can, on user input, spin up a runtime, load a 30Kb minified javascript library, do a bit of fuzzy text parsing, and results are instant.
My implementation is pretty minimal and dirty and wrong in dozens of ways. Evaluate strings, read the contents of variables, use JSON for interchange instead of doing it the more civilized way.
The documentation of QuickJS is mostly “just read the uncommented headers lol”, and there’s barely any example of QuickJS usage in the wild outside of Prototype, so it was much more difficult to get a minimal implementation working than the tiny implementation I have to show for it, but maybe someone will be interested in taking it further? Obviously, I can’t stress enough DSP code should never be written in JS, but it opens the door to all sorts of data processing that is a pain in C++ but a solved problem in the JS world.