How to create a Promise from a variable?

Question

I have a variable:

let x = 1;

What is the simplest way to create a Promise that will right away return the x ? Something like:

let promise = Promise(x);

The question is not about when and how to use Promises. It is clear.

what are you trying to achieve? `const p = Promise.resolve(x)` will directly resolve the promise so you could do smth like: `p.then(.....)` — messerbill, Sep 09 '20 at 09:47
Does this answer your question? [Why and when to use Promise.resolve?](https://stackoverflow.com/questions/54723849/why-and-when-to-use-promise-resolve) — Krzysztof Krzeszewski, Sep 09 '20 at 09:48
@KrzysztofKrzeszewski The question you mention is about something different. it is about when to use Promise.resolve, not about how to wrap variable into a Promise. — Tom Smykowski, Sep 09 '20 at 10:10

score 2 · Accepted Answer · answered Sep 09 '20 at 09:49

2

You make a resolved promise like this:

let x = 1;
let promise = Promise.resolve(x);

Also you can make a rejected promise:

let rejectedPromise = Promise.reject(x);

answered Sep 09 '20 at 09:49

Yoihito

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2
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score 1 · Answer 2 · answered Sep 09 '20 at 09:55

I agree with others Promise.resolve is a straightforward way to wrap a value into Promise. One more option is to use sync and async values inside function:

async function foo<T>(value: T): Promise<T> {
  // do something async
  // and/or return simple value
  return value;
}

const a: Promise<number> = foo(123);
const b: number = await foo(123);

How to create a Promise from a variable?

2 Answers2