String (docs.local.quickjs.Quickjs.String)

This library follows JavaScript semantics in most cases to ensure compatibility with the ECMA-262 specification:

Indices: All string indices are UTF-16 code unit positions, not byte positions. A string containing an emoji has length 2 (surrogate pair).

Not-found values: Methods like index_of return -1 when not found (JavaScript convention), not option (OCaml convention). This matches JavaScript's String.prototype.indexOf().

Character access: Methods like char_code_at return int option (OCaml convention) for bounds checking, since OCaml does not have JavaScript's implicit NaN coercion.

Negative indices: Methods like slice support negative indices counting from the end, matching JavaScript behavior.

type normalization =

Unicode normalization forms

val is_valid_utf8 : string -> bool

is_valid_utf8 s returns true if s contains only valid UTF-8 byte sequences. Use this for strict validation before processing untrusted input.

Note: All functions in this module handle invalid UTF-8 gracefully by replacing malformed sequences with U+FFFD (replacement character).

module Prototype : sig ... end

String.prototype methods

val lowercase_char : Uchar.t -> Uchar.t list

lowercase_char c converts a single character to lowercase. May return multiple characters for special cases.

val uppercase_char : Uchar.t -> Uchar.t list

uppercase_char c converts a single character to uppercase. May return multiple characters (e.g., ß -> SS).