20 - Promise.all

20 - Promise.all

by Anthony Fu (@antfu) #中等 #array #promise

题目

给函数PromiseAll指定类型，它接受元素为 Promise 或者类似 Promise 的对象的数组，返回值应为Promise<T>，其中T是这些 Promise 的结果组成的数组。

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

// 应推导出 `Promise<[number, 42, string]>`
const p = PromiseAll([promise1, promise2, promise3] as const)

在 Github 上查看：https://tsch.js.org/20/zh-CN

代码

/* _____________ 你的代码 _____________ */

declare function PromiseAll<T extends any[]>(values: [...T]): Promise<{ [K in keyof T]: Awaited<T[K]> }>

测试用例

/* _____________ 测试用例 _____________ */
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)])
const promiseAllTest4 = PromiseAll<Array<number | Promise<number>>>([1, 2, 3])
const promiseAllTest5 = PromiseAll<(number | Promise<string>)[]>([1, 2, Promise.resolve('3')])

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]>>>,
  Expect<Equal<typeof promiseAllTest4, Promise<number[]>>>,
  Expect<Equal<typeof promiseAllTest5, Promise<(number | string)[]>>>,
]

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