uniqBy (Functional Programming) ​
Creates a function that removes duplicates by a mapped key. Use it with pipe.
typescript
const result = pipe(array, uniqBy(mapper));INFO
Prefer the original es-toolkit uniqBy in ordinary code. Use this fp variant when composing transformations with pipe.
Usage ​
uniqBy keeps the first value for each key returned by mapper. It preserves the order of first occurrence and is lazy-capable inside pipe.
typescript
import { pipe, uniqBy } from 'es-toolkit/fp';
pipe(
[{ id: 1 }, { id: 1 }, { id: 2 }],
uniqBy(item => item.id)
); // => [{ id: 1 }, { id: 2 }]Parameters ​
mapper((item: T, index: number) => U): The function that returns the key used for uniqueness.
Returns ​
((array: readonly T[]) => T[]): A function that maps a readonly T[] to a duplicate-free array by key.