mapRight

Callable

• mapRight<E, T>(x: E, f: (r: E extends Right<R> ? R : never) => T): E extends Right<unknown> ? Right<T> : E

---

• Applies a transformation function to the Right value of an Either type, if present. If the input is a Left, it remains unchanged.

  Example

  mapRight({ right: 'bar' }, (x) => `${x}${x}`)
  // => { right: "barbar" }
  
  mapRight({ left: 'bar' }, (x) => `${x}${x}`)
  // => { left: "bar" }

  ---

  Type parameters

  • E: Either<unknown, unknown>

    The type of the Either.

  • T

    The type of the transformed Right value.

  Parameters

  • x: E

    The Either value to map.

  • f: (r: E extends Right<R> ? R : never) => T

    The transformation function to apply to the Right value.

  Returns E extends Right<unknown> ? Right<T> : E

  An Either object where the Right has been transformed if present, or the original Left.