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.
sig external length : 'a array -> int = "%array_length" external get : 'a array -> int -> 'a = "%array_safe_get" external set : 'a array -> int -> 'a -> unit = "%array_safe_set" external make : int -> 'a -> 'a array = "caml_make_vect" external create : int -> 'a -> 'a array = "caml_make_vect" val init : int -> f:(int -> 'a) -> 'a array val make_matrix : dimx:int -> dimy:int -> 'a -> 'a array array val create_matrix : dimx:int -> dimy:int -> 'a -> 'a array array val append : 'a array -> 'a array -> 'a array val concat : 'a array list -> 'a array val sub : 'a array -> pos:int -> len:int -> 'a array val copy : 'a array -> 'a array val fill : 'a array -> pos:int -> len:int -> 'a -> unit val blit : src:'a array -> src_pos:int -> dst:'a array -> dst_pos:int -> len:int -> unit val to_list : 'a array -> 'a list val of_list : 'a list -> 'a array val iter : f:('a -> unit) -> 'a array -> unit val map : f:('a -> 'b) -> 'a array -> 'b array val iteri : f:(int -> 'a -> unit) -> 'a array -> unit val mapi : f:(int -> 'a -> 'b) -> 'a array -> 'b array val fold_left : f:('a -> 'b -> 'a) -> init:'a -> 'b array -> 'a val fold_right : f:('b -> 'a -> 'a) -> 'b array -> init:'a -> 'a val sort : cmp:('a -> 'a -> int) -> 'a array -> unit val stable_sort : cmp:('a -> 'a -> int) -> 'a array -> unit val fast_sort : cmp:('a -> 'a -> int) -> 'a array -> unit external unsafe_get : 'a array -> int -> 'a = "%array_unsafe_get" external unsafe_set : 'a array -> int -> 'a -> unit = "%array_unsafe_set" end