type-challenges-judge

Type Challenges Judge

Problems

Progress

Mutable Keys

提出詳細

type MyEqual<X,Y> =
  (<T>() => T extends X ? 0 : 1) extends
  (<U>() => U extends Y ? 0 : 1) ? true : false
type IsMutable<T,K extends keyof T> =
  MyEqual<Pick<T,K>,Readonly<Pick<T,K>>> extends true ? false : true
type MutableKeys<T,K extends keyof T=keyof T> =
 K extends K ? IsMutable<T,K> extends true ? K : never : never

提出日時	2023-09-22 16:08:15
問題	Mutable Keys
ユーザー	sankantsu
ステータス	Accepted

テストケース

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

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