Standard Library
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 : bytes -> int = "%string_length" external get : bytes -> int -> char = "%string_safe_get" external set : bytes -> int -> char -> unit = "%string_safe_set" external create : int -> bytes = "caml_create_string" val make : int -> char -> bytes val init : int -> f:(int -> char) -> bytes val empty : bytes val copy : bytes -> bytes val of_string : string -> bytes val to_string : bytes -> string val sub : bytes -> pos:int -> len:int -> bytes val sub_string : bytes -> int -> int -> string val fill : bytes -> pos:int -> len:int -> char -> unit val blit : src:bytes -> src_pos:int -> dst:bytes -> dst_pos:int -> len:int -> unit val concat : sep:bytes -> bytes list -> bytes val iter : f:(char -> unit) -> bytes -> unit val iteri : f:(int -> char -> unit) -> bytes -> unit val map : f:(char -> char) -> bytes -> bytes val mapi : f:(int -> char -> char) -> bytes -> bytes val trim : bytes -> bytes val escaped : bytes -> bytes val index : bytes -> char -> int val rindex : bytes -> char -> int val index_from : bytes -> int -> char -> int val rindex_from : bytes -> int -> char -> int val contains : bytes -> char -> bool val contains_from : bytes -> int -> char -> bool val rcontains_from : bytes -> int -> char -> bool val uppercase : bytes -> bytes val lowercase : bytes -> bytes val capitalize : bytes -> bytes val uncapitalize : bytes -> bytes type t = bytes val compare : BytesLabels.t -> BytesLabels.t -> int external unsafe_get : bytes -> int -> char = "%string_unsafe_get" external unsafe_set : bytes -> int -> char -> unit = "%string_unsafe_set" external unsafe_blit : src:bytes -> src_pos:int -> dst:bytes -> dst_pos:int -> len:int -> unit = "caml_blit_string" "noalloc" external unsafe_fill : bytes -> pos:int -> len:int -> char -> unit = "caml_fill_string" "noalloc" val unsafe_to_string : bytes -> string val unsafe_of_string : string -> bytes end