Does JavaScript async Function Implicitly Return a Promise?

Find out whether an async function returns a Promise or not in JavaScript

The short answer is YES; a return value from an async function always returns a Promise implicitly. To demonstrate this, let's output the return value of an async function without await:

async function foo() {
    return 'foobar';
}

console.log(foo()); // output: Promise {<fulfilled>: "foobar"}

This is also true when the async function has no return value. In that case, we get a Promise object resolved with undefined. For example:

async function foo() {}

console.log(foo()); // output: Promise {<fulfilled>: undefined}

Similarly, a rejected Promise is implicitly returned when an error is thrown inside an async function. For example:

async function foo() {
    throw new Error('foobar');
}

console.log(foo()); // output: Promise {<rejected>: Error: foobar}

It may also be worth mentioning that returning a Promise explicitly inside an async function won't return a Promise of a Promise but rather a single Promise with resolved/rejected value.

Check out our other post if you want to learn more about different states (and fates) of a JavaScript Promise.


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