For what I know (I've mentioned it in the first part[0]), the nspell[1] is the most close to "port (some) of Hunspell", and typo.js[2] ports even less (but might be enough for some, we used it in my previous company: it uses dictionaries for lookup, but uses its own simplistic suggest, which I needed to tweak a lot).

SymSpell algorithm (which is quite different, I'll go into it in the next part to some extent) is much easier to port, so there is a JS SymSpell port[3] (which seems abandoned though).

0: https://zverok.github.io/blog/2021-01-05-spellchecker-1.html

1: https://github.com/wooorm/nspell

2: https://github.com/cfinke/Typo.js/

3: https://github.com/IceCreamYou/SymSpell