Promise.all 与对象一起使用的打字稿类型

Question

There is a counterpart for Promise.all waiting for all promises in object. Sample implementation: https://www.npmjs.com/package/promise-all

Usage:

await promiseAll({ 
    key1: Promise.resolve(1), 
    key2: Promise.resolve(2) 
});

I wanted to write typings for such function. I tried using keyof but after a while, I noticed that I would somehow need to "unwrap" a type of a Promise which I doubt is possible.

Here's what I came with which is actually just an identity mapping now :D

function promiseAll(o: object): { [P in keyof typeof o]: typeof o[P] } {
...
}

Any ideas?

Answer 1

Hah, I figured it out!

type Promised<T> = { [P in keyof T]: PromiseLike<T[P]> };
function promiseAll<T>(o: Promised<T>): T {
  ...
}