TypeScript: Emulate Awaited built-in
13 August 2023 (Updated 13 August 2023)
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Solution
type MyAwaited<T> = T extends PromiseLike<infer U> ? MyAwaited<U> : T
/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils'
type X = Promise<string>
type Y = Promise<{ field: number }>
type Z = Promise<Promise<string | number>>
type Z1 = Promise<Promise<Promise<string | boolean>>>
type T = { then: (onfulfilled: (arg: number) => any) => any }
type cases = [
Expect<Equal<MyAwaited<X>, string>>,
Expect<Equal<MyAwaited<Y>, { field: number }>>,
Expect<Equal<MyAwaited<Z>, string | number>>,
Expect<Equal<MyAwaited<Z1>, string | boolean>>,
Expect<Equal<MyAwaited<T>, number>>,TypeScript playground
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TypeScript