Async Await with Timeout

It’s not trivial to put a timeout on an async process.

But, here is how you do it.

Let’s say we have some delay function defined like this one:

async function delay(ms) {
    return new Promise((res, rej) => {
        setTimeout(() => {
            res()
        }, ms)
    })
}

It’s quite a handy function, considering using it like await delay(1000)

And extend this function to get a timeout function like this:

async function timeout(ms) {
    await delay(ms)
    throw new Error('timeout')
}

Suppose you have some long running function around which you want to have a timeout:

async function longRunning() {
    ...
}

Obviously, you will call it this way await longRunning().

Now, you can put a timeout around it using Promise.race, which is a handy function to get only the one that resolved earliest, this way:

const res = await Promise.race([
    longRunning(),
    timeout(1000)
])

You now have it ! In a normal case, longRunning() is expected to be resolved earlier than timeout(1000) and the const res is the return value of that longRunning() function, but when the timeout(1000) is resolved earlier, it throws causing await Proimse.race to throw as well, no return value recorded.