Correct typescript async await syntax with typed arrow functions

Question

Similar question for vanilla JS here. I however want to use async await with typescript function as below.

Javascript

const foo = async () => {
  // do something
}

Initial attempt

export const fetchAirports = async (): Airport[] => {
  //More code
  return airports;
};

but i get an error ts(1055) Type 'Airport[]' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value. which to me sounds like a lot of jargon. Please remember I have to specify a return type in the function declaration otherwise it nullifies the need for typescript in the first place.

JavaScript async function will always return a Promise. Try changing the return type Airport[] you specified to Promise<Airport[]> — Max Lysenko
– Max Lysenko, Commented Oct 22, 2022 at 8:46
It's not a syntax problem, it's a type problem. An async function cannot return something that's not a promise. — jonrsharpe
– jonrsharpe, Commented Oct 22, 2022 at 8:50

Saurav Ghimire · Accepted Answer · 2022-10-22 08:49:55Z

4

Try this

export const fetchAirports = async (): Promise<Airport[]> => {
    //More code
    return airports;
}

Or

export const fetchAirports = async (): Promise<Array<Airport>> => {
    //More code
    return airports;
}

answered Oct 22, 2022 at 8:49

Saurav Ghimire

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Comments

Medlide · Accepted Answer · 2022-10-22 08:52:36Z

2

When you use async function, it wraps return value in Promise, so instead Airport[] you should wrap it in Promise like this: Promise<Airport[]>

answered Oct 22, 2022 at 8:52

Medlide

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