flatMapDepth

INFO

This function is only available in es-toolkit/compat for compatibility reasons. It either has alternative native JavaScript APIs or isn't fully optimized yet.

When imported from es-toolkit/compat, it behaves exactly like lodash and provides the same functionalities, as detailed here.

Maps each element in an array or object using an iteratee function and flattens the result up to the specified depth.

Signature

function flatMapDepth<T>(
  collection:
    | Record<string, ArrayLike<T | RecursiveArray<T>> | T>
    | Record<number, ArrayLike<T | RecursiveArray<T>> | T>
    | null
    | undefined
): T[];

function flatMapDepth<T, R>(
  array: ArrayLike<T> | null | undefined,
  iteratee: (value: T, index: number, array: ArrayLike<T>) => ArrayLike<R | RecursiveArray<R>> | R,
  depth?: number
): R[];

function flatMapDepth<T extends object, R>(
  collection: T,
  iteratee: (value: T[keyof T], key: string, object: T) => ArrayLike<R | RecursiveArray<R>> | R,
  depth?: number
): R[];

function flatMapDepth(collection: object | null | undefined, path: string, depth?: number): any[];

function flatMapDepth(collection: object | null | undefined, matches: object, depth?: number): boolean[];

Parameters

• collection (Record<string, ArrayLike<T | RecursiveArray<T>> | T> | Record<number, ArrayLike<T | RecursiveArray<T>> | T> | null | undefined): The array or object to iterate over.
• iteratee: The function invoked per iteration. Defaults to identity.
  • (value: T, index: number, array: ArrayLike<T>) => ArrayLike<R | RecursiveArray<R>> | R: Function called for each element.
  • (value: T[keyof T], key: string, object: T) => ArrayLike<R | RecursiveArray<R>> | R: Function called for each property.
  • string: The path of the property to extract.
  • object: The object to match against.
• depth (number): The maximum recursion depth. Defaults to 1.

Returns

• (T[] | R[] | any[] | boolean[]): Returns the new flattened array.

Examples

import { flatMapDepth } from 'es-toolkit/compat';

// Basic example with a function returning arrays
function duplicate(n) {
  return [n, n];
}

flatMapDepth([1, 2], duplicate);
// => [1, 1, 2, 2]

// Specifying depth
flatMapDepth(
  [
    [
      [1, 2],
      [3, 4],
    ],
  ],
  n => [n, n],
  2
);
// => [1, 1, 2, 2, 3, 3, 4, 4]

// Using matches object
flatMapDepth({ a: 1, b: 2 }, { a: 1 });
// => [true, false]

// Using property path
flatMapDepth({ a: { a: 1, b: 2 } }, 'a');
// => [1, 2]