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Required Keys

提出詳細

type IsRequired<T, K extends PropertyKey> = Omit<T, K> extends T ? false : true

type GetRequiredKeys<K extends PropertyKey, T> = K extends any
  ? IsRequired<T, K> extends true
    ? K
    : never
  : never;

type RequiredKeys<T> = GetRequiredKeys<keyof T, T>
提出日時2023-08-13 12:26:45
問題Required Keys
ユーザーtekihei2317
ステータスAccepted
テストケース
import type { Equal, Expect } from '@type-challenges/utils'

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