type-challenges-judge

Type Challenges Judge

Problems

Progress

Optional Keys

提出詳細

type OptionalKeys<T extends object> = keyof {
  [P in keyof T as {} extends Pick<T, P> ? P:never]: T[P];
};

提出日時	2022-07-01 00:14:32
問題	Optional Keys
ユーザー	waki285
ステータス	Accepted

テストケース

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>>,
]