xorBy (Functional Programming)

Creates a function that returns the symmetric difference by a mapped key. Use it with pipe.

const result = pipe(array, xorBy(secondArray, mapper));

::: info

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

:::

Usage

xorBy compares the values returned by mapper and returns values whose mapped key appears in exactly one array.

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

pipe(
  [{ id: 1 }, { id: 2 }],
  xorBy([{ id: 2 }, { id: 3 }], item => item.id)
); // => [{ id: 1 }, { id: 3 }]

Parameters

• secondArray (readonly T[]): The array to compare with the piped array.
• mapper ((item: T) => U): The function that returns the comparison key.

Returns

((array: readonly T[]) => T[]): A function that maps a readonly T[] to the symmetric difference by key.