[Typescript] 23. Medium - Promise.all

Type the function PromiseAll that accepts an array of PromiseLike objects, the returning value should be Promise<T> where T is the resolved result array.

const promise1 = Promise.resolve(3);
const promise2 = 42;
const promise3 = new Promise<string>((resolve, reject) => {
  setTimeout(resolve, 100, 'foo');
});

// expected to be `Promise<[number, 42, string]>`
const p = PromiseAll([promise1, promise2, promise3] as const)

https://ghaiklor.github.io/type-challenges-solutions/en/medium-promise-all.html

/* _____________ Your Code Here _____________ */

declare function PromiseAll<T extends unknown[]>(values: readonly [...T]): Promise<{[P in keyof T]: T[P] extends Promise<infer R> ? R : T[P]}>;


/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

const promiseAllTest1 = PromiseAll([1, 2, 3] as const)
const promiseAllTest2 = PromiseAll([1, 2, Promise.resolve(3)] as const)
const promiseAllTest3 = PromiseAll([1, 2, Promise.resolve(3)])
type x = typeof promiseAllTest2
type cases = [
  Expect<Equal<typeof promiseAllTest1, Promise<[1, 2, 3]>>>,
  Expect<Equal<typeof promiseAllTest2, Promise<[1, 2, number]>>>,
  Expect<Equal<typeof promiseAllTest3, Promise<[number, number, number]>>>,
]

• Variadic Tuple Types: (values: readonly [...T])
• Mapped Types: [P in keyof T]: ...
• Index Types
• Conditional Types
• Type inference in conditional types

标签：Typescript,const,resolve,_____________,PromiseAll,Medium,Promise,type
来源： https://www.cnblogs.com/Answer1215/p/16672831.html