flatMapDeep (Functional Programming)

Creates a function that maps each value and deeply flattens the result. Use it with pipe.

const result = pipe(array, flatMapDeep(iteratee));

INFO

Prefer the original es-toolkit flatMapDeep in ordinary code. Use this fp variant when composing transformations with pipe.

Usage

flatMapDeep calls iteratee for each value in the piped array and recursively flattens the returned arrays.

import { flatMapDeep, pipe } from 'es-toolkit/fp';

pipe(
  [1, 2],
  flatMapDeep(value => [[value, value]])
); // => [1, 1, 2, 2]

Parameters

• iteratee ((item: T, index: number) => U): The function that maps each value before deep flattening.

Returns

((array: readonly T[]) => Array<ExtractNestedArrayType<U>>): A function that maps a readonly T[] to a deeply flattened array.