First of Array
提出詳細
type First<T extends unknown[]> = T extends [] ? never : T[0]
提出日時 | 2023-04-28 23:03:21 |
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問題 | First of Array |
ユーザー | Dowanna |
ステータス | Accepted |
import type { Equal, Expect } from '@type-challenges/utils' type cases = [ Expect<Equal<First<[3, 2, 1]>, 3>>, Expect<Equal<First<[() => 123, { a: string }]>, () => 123>>, Expect<Equal<First<[]>, never>>, Expect<Equal<First<[undefined]>, undefined>>, ] type errors = [ // @ts-expect-error First<'notArray'>, // @ts-expect-error First<{ 0: 'arrayLike' }>, ]