[Typescript] 54. Medium - Tuple to Nested Object

Given a tuple type T that only contains string type, and a type U, build an object recursively.

type a = TupleToNestedObject<['a'], string> // {a: string}
type b = TupleToNestedObject<['a', 'b'], number> // {a: {b: number}}
type c = TupleToNestedObject<[], boolean> // boolean. if the tuple is empty, just return the U type

 

/* _____________ Your Code Here _____________ */

type TupleToNestedObject<T extends any[], U> = T extends [infer A extends string, ...(infer REST)]
  ? {[Key in A]: TupleToNestedObject<REST, U>}
  : U

type x = TupleToNestedObject<['a', 'b'], number>
/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<TupleToNestedObject<['a'], string>, { a: string }>>,
  Expect<Equal<TupleToNestedObject<['a', 'b'], number>, { a: { b: number } }>>,
  Expect<Equal<TupleToNestedObject<['a', 'b', 'c'], boolean>, { a: { b: { c: boolean } } }>>,
  Expect<Equal<TupleToNestedObject<[], boolean>, boolean>>,
]