uniqBy

uniqBy() function

Unlike uniq returns Iterable/AsyncIterable with duplicate values removed by applying with f inside the given Iterable/AsyncIterable.

Signature:

declare function uniqBy<A, B>(f: (a: A) => B, iterable: Iterable<A>): IterableIterator<A>;

declare function uniqBy<A, B>(f: (a: A) => B, iterable: AsyncIterable<A>): AsyncIterableIterator<A>;

declare function uniqBy<A extends Iterable<unknown> | AsyncIterable<unknown>, B>(f: (a: IterableInfer<A>) => B, iterable?: A): (iterable: A) => ReturnIterableIteratorType<A>;

Example

const iter = uniqBy(a => a.age, [{age: 21}, {age: 23}, {age: 21}, {age: 34}]);
iter.next() // {done:false, value: {age: 21}}
iter.next() // {done:false, value: {age: 23}}
iter.next() // {done:false, value: {age: 34}}
iter.next() // {done:true, value: undefined}

// with pipe
pipe(
 [{age: 21}, {age: 23}, {age: 21}, {age: 34}],
 uniqBy(a => a.age),
 toArray,
); // [{age: 21}, {age: 23}, {age: 34}]

await pipe(
 Promise.resolve([{age: 21}, {age: 23}, {age: 21}, {age: 34}]),
 uniqBy(a => a.age),
 toArray,
); // [{age: 21}, {age: 23}, {age: 34}]

// if you want to use asynchronous callback
await pipe(
 Promise.resolve([{age: 21}, {age: 23}, {age: 21}, {age: 34}]),
 toAsync,
 uniqBy(async (a) => a.age),
 toArray,
); // [{age: 21}, {age: 23}, {age: 34}]

// toAsync
await pipe(
 [Promise.resolve({age: 21}), Promise.resolve({age: 23}), Promise.resolve({age: 21}), Promise.resolve({age: 34})],
 toAsync,
 uniqBy(a => a.age),
 toArray,
); // [{age: 21}, {age: 23}, {age: 34}]

Try It

see pipe, toAsync, toArray