题目

Github: Promise.all

传入函数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)

Answer

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