Thank you for the encouragement! Avoiding alignment gaps is indeed pretty great: I have a vision of packing Arrays into 9 bytes split over two or three cache lines.

On typed indexes: If we accept only about 2^24 possible index values then we could use a 32 bit integer for our Values, or at least for Objects (if we want to keep 7 bytes worth of stack data, which is pretty hard to pass on).

I love the comments comparing Nova to V8: That's what I want to aim for after all :) I'm not sure I've heard of Fabrice Bellard's JS engine, thanks, I'll take a look!

Your blog mentions QuickJS, which I believe is the mentioned engine by Fabrice