I'm very much not a serious OCaml:er but when I've dabbled some in it I got the impression that their "standard library" is kind of the de facto standard library.
They had Core. Base is their new attempt at sort of a "standard" lib. Not all OCaml-ers use JS libs though. There are some Batteries users out there. When I do Advent of Code, I almost always try to do it with OCaml's built in standard lib.
