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00189-easy-awaited.ts
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00189-easy-awaited.ts
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/*
189 - Awaited
-------
by Maciej Sikora (@maciejsikora) #easy #promise #built-in
### Question
If we have a type which is wrapped type like Promise. How we can get a type which is inside the wrapped type? For example if we have `Promise<ExampleType>` how to get ExampleType?
> This question is ported from the [original article](https://dev.to/macsikora/advanced-typescript-exercises-question-1-45k4) by [@maciejsikora](https://github.com/maciejsikora)
> View on GitHub: https://tsch.js.org/189
*/
/* _____________ Your Code Here _____________ */
type MyAwaited<T extends Promise<unknown>> = T extends Promise<infer U> ? (U extends Promise<unknown> ? MyAwaited<U>: U) : never;
/* _____________ 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 cases = [
Expect<Equal<MyAwaited<X>, string>>,
Expect<Equal<MyAwaited<Y>, { field: number }>>,
Expect<Equal<MyAwaited<Z>, string | number>>,
Expect<Equal<MyAwaited<Z1>, string | boolean>>
];
// @ts-expect-error
type error = MyAwaited<number>;
/* _____________ Further Steps _____________ */
/*
> Share your solutions: https://tsch.js.org/189/answer
> View solutions: https://tsch.js.org/189/solutions
> More Challenges: https://tsch.js.org
*/