In async functions, do we return X, or do we return "Promise.Resolve(X)"?

Question

This is something I have never quite been able to nail down.

Consider an async function in Typescript. Which is correct?

async function asyncFunctionOne(string1: string, string2: string, string3: string) {
    var returnObject1 = new object {
        fieldOne: object1,
        fieldTwo: object2,
        fieldThree: object3
    }

    return Promise.resolve(returnObject1)
}

async function asyncFunctionTwo(string1: string, string2: string, string3: string) {
    var returnObject2 = new object {
        fieldOne: object1,
        fieldTwo: object2,
        fieldThree: object3
    }

    return returnObject2;
}

Additionally, consider we were calling this function and we needed the response for something further in our program. Would we need to await the first function, the second function, both, or neither?

There's no need to wrap the return value in a promise. But you can return a promise... — MinusFour, Oct 14 '21 at 17:54
Try them out and see what happens. - e.g. `console.log` the results — Adam Jenkins, Oct 14 '21 at 17:54
The thing is that `Promise>` is `Promise`. Because Promise is [monad](https://en.wikipedia.org/wiki/Monad_(functional_programming)). — Yury Tarabanko, Oct 14 '21 at 17:56
You only need to make a function `async` if you use `await` inside. A function that returns a promise doesn't need to be async. — , Oct 14 '21 at 17:58

score 2 · Answer 1 · answered Oct 14 '21 at 18:02

That async functions always return a promise. A plain return value will be wrapped with a resolved promise always. Observe in the following code that the same result can be obtained either using await or Promise.then.

(async function() {

   async function asyncFunctionTwo() {
      return 999;
   }


   asyncFunctionTwo().then((val => console.log(val)));
   
   //OR
   
   console.log(await asyncFunctionTwo())

})();

In async functions, do we return X, or do we return "Promise.Resolve(X)"?

1 Answers1