While loop with an async setTimeout function

Question

I have a problem. My code doesn't work. It doesn't display the last essage in the console.log (the "end"). I use a setTimeout promise to do one thing every 3000ms. Here is my promise function setTimeOut

function delay(message){
    return new Promise(() => setTimeout(function () {
        console.log(message)
    }, 3000))
}

That I use in an async function in my code :

async () => {
    while (true) {
        console.log("Start")
        await delay("No")
        console.log("End")
    }
}

I make my code more easier (without all the conditions and the functions that I have to call) because I think I've missed something in my understanding of the promise maybe. What am i doing wrong?

Could you please help me for this?

Where’s the definition of timeout and where is delay used? You forgot to resolve the promise in delay. — Sebastian Simon
– Sebastian Simon, Commented Aug 31, 2020 at 18:16
Sorry, I changed the name of the function to post it, but timeout and delay are the same function — Islero
– Islero, Commented Aug 31, 2020 at 18:22

akinuri · Accepted Answer · 2022-12-29 18:22:26Z

3

Your promise in delay/timeout function never resolves.

Here's how it will work. Note the resolve parameter of the promise callback.

function delay(message) {
    return new Promise((resolve) => setTimeout(function () {
        console.log(message);
        resolve();
    }, 3000))
}
    
(async () => {
    while (true) {
        console.log("Start")
        await delay("No")
        console.log("End")
    }
})();

edited Dec 29, 2022 at 18:22

akinuri

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answered Aug 31, 2020 at 18:25

fjc

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2 Comments

Islero Over a year ago

Ok, I got it, thank you for your help. I misuse the promise, now I'm starting to understand how it works.

akinuri Over a year ago

I just had an issue with an while + async function use. Doing a DOM manipulation and checking the result repeatedly in while gives incorrect results. Probably due to the render time. I solved the issue with a recursive approach, but this is more practical. Adding a delay after the modification works.

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