L0v3ch4n

外观

IsRequiredKey

约 145 字小于 1 分钟

2026-02-11

题目

Implement a generic IsRequiredKey<T, K> that return whether K are required keys of T .

For example

type A = IsRequiredKey<{ a: number, b?: string },'a'> // true
type B = IsRequiredKey<{ a: number, b?: string },'b'> // false
type C = IsRequiredKey<{ a: number, b?: string },'b' | 'a'> // false

解题思路

待补充

答案

type IsRequiredKey<T, K extends keyof T> = any

验证

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

type cases = [
  Expect<Equal<IsRequiredKey<{ a: number, b?: string }, 'a'>, true>>,
  Expect<Equal<IsRequiredKey<{ a: undefined, b: string }, 'a'>, true>>,
  Expect<Equal<IsRequiredKey<{ a: number, b?: string }, 'b'>, false>>,
  Expect<Equal<IsRequiredKey<{ a: number, b?: string }, 'b' | 'a'>, false>>,
  Expect<Equal<IsRequiredKey<{ a: undefined, b: undefined }, 'b' | 'a'>, true>>,
]

参考

无