Promise.resolve() inside async function

Question

I read a SO thread somewhere a while back that using static Promise methods like Promise.resolve() or Promise.reject() inside an async function are anti-patterns but I can't seem to find it.

Given the following:

const asyncFunc = async (foo) => {
    if (foo) return Promise.resolve()

    return Promise.reject()
}

Is this considered an anti-pattern?

Answer 1

Using Promise.resolve is, perhaps not so much an antipattern so much as completely unnecessary, because returning a plain value from an async function will result in the Promise that it returns resolving to that value.

if (foo) return Promise.resolve()

is equivalent to

if (foo) return;

and

if (foo) return Promise.resolve(5)

is equivalent to

if (foo) return 5;

So you may as well leave off the Promise.resolve.

Promise.reject is a bit different. If you want to reject the Promise that the function returns, you may either do throw <expression>, or you may do return Promise.reject<expression> - both are equivalent, and I don't think there's any concrete reason to prefer one or the other in all circumstances (though I'd prefer throw since it's more concise).