union (Functional Programming)

Creates a function that combines two arrays without duplicate values. Use it with pipe.

const result = pipe(array, union(secondArray));

::: info

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

:::

Usage

union returns unique values from the piped array followed by values from secondArray that have not appeared yet.

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

pipe([1, 2, 2], union([2, 3])); // => [1, 2, 3]

Parameters

• secondArray (readonly T[]): The array to combine after the piped array.

Returns

((array: readonly T[]) => T[]): A function that maps a readonly T[] to the union of both arrays.