Unbox

约 314 字大约 1 分钟

2026-02-11

题目

How can we build a type that "unboxes" arrays, functions, promises, and tuples?

Example:

Unbox<string> // string
Unbox<()=>number> // number
Unbox<boolean[]> // boolean
Unbox<Promise<boolean>> // boolean

Bonus: Can we make it recursive?

Unbox<() => () => () => () => number> // number

Double Bonus: Can we control the recursion?

Unbox<() => () => () => () => number, 3> // () => number

解题思路

待补充

答案

type Unbox<T> = any

验证

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

type cases = [
  // Base cases
  Expect<Equal<Unbox<number>, number>>,
  Expect<Equal<Unbox<() => number>, number>>,
  Expect<Equal<Unbox<() => number | string>, number | string>>,
  Expect<Equal<Unbox<number[]>, number>>,
  Expect<Equal<Unbox<(number | string)[]>, number | string>>,
  Expect<Equal<Unbox<[number]>, number>>,
  Expect<Equal<Unbox<Promise<number>>, number>>,

  // Bonus: Recursion
  Expect<Equal<Unbox<() => Promise<() => Array<Promise<boolean>>>>, boolean>>,

  // Bonus: Recursion levels
  Expect<Equal<Unbox<() => () => () => () => number, 0>, number>>,
  Expect<Equal<Unbox<() => () => () => () => number, 1>, () => () => () => number>>,
  Expect<Equal<Unbox<() => () => () => () => number, 2>, () => () => number>>,
  Expect<Equal<Unbox<() => () => () => () => number, 3>, () => number>>,
  Expect<Equal<Unbox<() => () => () => () => number, 4>, number>>,
  Expect<Equal<Unbox<() => () => () => () => number, 5>, number>>,
  Expect<Equal<Unbox<number[][][][], 0>, number>>,
  Expect<Equal<Unbox<number[][][][], 1>, number[][][]>>,
  Expect<Equal<Unbox<number[][][][], 2>, number[][]>>,
  Expect<Equal<Unbox<number[][][][], 3>, number[]>>,
  Expect<Equal<Unbox<number[][][][], 4>, number>>,
  Expect<Equal<Unbox<number[][][][], 5>, number>>,
  Expect<Equal<Unbox<[[[[number]]]], 0>, number>>,
  Expect<Equal<Unbox<[[[[number]]]], 1>, [[[number]]]>>,
  Expect<Equal<Unbox<[[[[number]]]], 2>, [[number]]>>,
  Expect<Equal<Unbox<[[[[number]]]], 3>, [number]>>,
  Expect<Equal<Unbox<[[[[number]]]], 4>, number>>,
  Expect<Equal<Unbox<[[[[number]]]], 5>, number>>,
  Expect<Equal<Unbox<Promise<Promise<Promise<number>>>, 0>, number>>,
  Expect<Equal<Unbox<Promise<Promise<Promise<number>>>, 1>, Promise<Promise<number>>>>,
  Expect<Equal<Unbox<Promise<Promise<Promise<number>>>, 2>, Promise<number>>>,
  Expect<Equal<Unbox<Promise<Promise<Promise<number>>>, 3>, number>>,
  Expect<Equal<Unbox<Promise<Promise<Promise<number>>>, 4>, number>>,
]

参考

无