5153 - IndexOf

5153 - IndexOf

by Pineapple (@Pineapple0919) #中等 #array

题目

Implement the type version of Array.indexOf, indexOf<T, U> takes an Array T, any U and returns the index of the first U in Array T.

type Res = IndexOf<[1, 2, 3], 2>; // expected to be 1
type Res1 = IndexOf<[2,6, 3,8,4,1,7, 3,9], 3>; // expected to be 2
type Res2 = IndexOf<[0, 0, 0], 2>; // expected to be -1

在 Github 上查看：https://tsch.js.org/5153/zh-CN

代码

/* _____________ 你的代码 _____________ */

type IndexOf<T, U, I extends any[] = []> = T extends [infer F, ...infer Rest]
  ? Equal<F, U> extends true
    ? I['length']
    : IndexOf<Rest, U, [...I, 1]>
  : -1

测试用例

/* _____________ 测试用例 _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<IndexOf<[1, 2, 3], 2>, 1>>,
  Expect<Equal<IndexOf<[2, 6, 3, 8, 4, 1, 7, 3, 9], 3>, 2>>,
  Expect<Equal<IndexOf<[0, 0, 0], 2>, -1>>,
  Expect<Equal<IndexOf<[string, 1, number, 'a'], number>, 2>>,
  Expect<Equal<IndexOf<[string, 1, number, 'a', any], any>, 4>>,
  Expect<Equal<IndexOf<[string, 'a'], 'a'>, 1>>,
  Expect<Equal<IndexOf<[any, 1], 1>, 1>>,
]

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