L0v3ch4n

外观

Mutable Keys

约 117 字小于 1 分钟

2026-02-11

题目

Implement the advanced util type MutableKeys<T>, which picks all the mutable (not readonly) keys into a union.

For example:

type Keys = MutableKeys<{ readonly foo: string; bar: number }>;
// expected to be “bar”

解题思路

待补充

答案

type MutableKeys<T> = any

验证

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>>,
]

参考

无