anonn – 15-18 Oct 10

Aanonn

10/10/2022

Hi, I have trouble understanding how promises work in terms of the event loop.

function a() {
    console.log('a')
}

function b() {
  console.log("b");
}

function c() {
  console.log("c")
}

fetch("https://fakelinkabcabc.com").catch(a);

Promise.resolve().then(b);

Promise.reject().catch(c);

function a() {
    console.log('a')
}

function b() {
  console.log("b");
}

function c() {
  console.log("c")
}

fetch("https://fakelinkabcabc.com").catch(a);

Promise.resolve().then(b);

Promise.reject().catch(c);

Why is the output b,c,a Could someone explain in terms of the event loop? e.g the image attached What actually happens when the javascript engine reaches Promise.resolve()? What actually happens when the .then(b) is reached? I have been unable to find resources that go through step by step how interacting with Promises/Web APIs work in terms of the event loop and would be very happy if someone could point me some resources

EEvokeMe

10/10/2022

https://www.jsv9000.app

Aanonn

10/10/2022

That is actually where I got the example, but I am still confused. So step 1, b gets put into the microtask queue. How does it get there? What does Promise.resolve() do in terms of the event loop? What does .then() do in terms of the event loop? Who puts b into the microtask queue? Is it the Web API?

EEvokeMe

10/10/2022

There is about sections. U can read about it.

Aanonn

10/10/2022

I am confused by

Promise.resolve()
.then(() => console.log('hi'));

Promise.resolve()
.then(() => console.log('hi'));

So the javascript engine sees Promise.resolve() and returns a fulfilled promise. We go to the next line, .then(() => console.log('hi'));. What is the step by step process that happens now? e.g does the javascript engine see that the attached promise is resolved then throw the arrow function to the microtask queue?

EEvokeMe

10/10/2022

It's just fn (reaction on resolved promise) that microtask. I think in about section pretty good description.

UUUnknown User

10/11/2022

2 Messages Not Public

Looking for more? Join the community!

anonn – 15-18 Oct 10

anonn – 15-18 Oct 10

Want results from more Discord servers?

Add your server

Recommended Posts

✅ – vauld – 19-04 Oct 9has anyone worked with commerceJS?✅ – venus – 12-02 Oct 9Looking for possible regex solution, since I still suck at it. The goal of the regex is to validate setInterval without destroying it to update state?I have a perdicament where I want to update state on an interval. Every way that I go about it I fin devTej – 15-10 Oct 8I read react 18 documentation, that component will render twice for future features. `This featur ✅ – Hailwood – 00-51 Oct 7Can someone please help me with some regex - Given strings like ``` "this definitely will not match ✅ – Cosec – 16-19 Oct 5how to have a css/js selector using both id and name?✅ – BIOLOGY SCIENCE – 14-32 Oct 5[Audio API] Audio doesn't play when I use createMediaElementSource on an audio element. (more info +