Below is the API for the OCaml standard library. It's directly copied over from the OCaml Manual, formatted to the Reason syntax and styled accordingly. The API docs are work-in-progress; we'll be polishing these gradually!
If you're targeting JavaScript, the API docs for BuckleScript includes all of below, plus JS-specific APIs.
module type S = sig .. end
type key
type 'a t
val create : int -> 'a t
val clear : 'a t -> unit
val reset : 'a t -> unit
val copy : 'a t -> 'a t
val add : 'a t -> key:key -> data:'a -> unit
val remove : 'a t -> key -> unit
val find : 'a t -> key -> 'a
val find_all : 'a t -> key -> 'a list
val replace : 'a t -> key:key -> data:'a -> unit
val mem : 'a t -> key -> bool
val iter : f:(key:key -> data:'a -> unit) -> 'a t -> unit
val fold : f:(key:key -> data:'a -> 'b -> 'b) -> 'a t -> init:'b -> 'b
val length : 'a t -> int
val stats : 'a t -> MoreLabels.Hashtbl.statistics