TypeScript 온라인

00090-hard-optional-keys
Hard
utils

챌린지 출처: type-challenges/00090-hard-optional-keys

Implement the advanced util type OptionalKeys<T>, which picks all the optional keys into a union.

Loading...

테스트 케이스 출처: type-challenges/00090-hard-optional-keys/test-cases.ts

import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<OptionalKeys<{ a: number, b?: string }>, 'b'>>,
  Expect<Equal<OptionalKeys<{ a: undefined, b?: undefined }>, 'b'>>,
  Expect<Equal<OptionalKeys<{ a: undefined, b?: undefined, c?: string, d?: null }>, 'b' | 'c' | 'd'>>,
  Expect<Equal<OptionalKeys<{}>, never>>,
]