Typescript类型体操 - Promise.all

题目

中文

键入函数PromiseAll，它接受PromiseLike对象数组，返回值应为Promise<T>，其中T是解析的结果数组。

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)

English

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)

答案

declare function PromiseAll<T extends any[]>(values: readonly [...T]): Promise<{[K in keyof T]: T[K] extends PromiseLike<infer U> ? U : T[K]}>

在线演示