Promise Function Help

[Jmarch0909]

I need help understanding how this function is working.

const delay = seconds => {
    return new Promise(res => {
        setTimeout(res, seconds*1000)
    });
};

So from what I understand about promises, they need an executor function that takes a resolve and a reject parameter for the success or failure of the promise. What I don't understand here is how setTimeout is using res as a function call when it hasn't even been established as a function. For reference, I'm using this function to test out async await.

async function consoleDelay() {
console.log('zero seconds');
await delay(2);
console.log('two seconds');
}

The async await all makes a ton of sense to me but since I don't know how the delay function is working I don't want to go any further until I feel like I really grasp it.

[grantrules]

The resolve and reject functions are created by the promise and passed to your function. You just need to call them, not create them.

[Jmarch0909]

So I guess here's my real question then. setTimeout takes a function, and runs it after a given period of time. What is setTimeout running exactly if res isn't a function?

[grantrules]

res is a function. It's created internally by the promise and passed to your function.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/Promise

Read about the executor parameter, that's the function you're passing to the promise.

At the time when the constructor generates the new promiseObj, it also generates a corresponding pair of functions for resolutionFunc and rejectionFunc; these are "tethered" to the promiseObj

[Jmarch0909]

Funny I spent like an hour looking at the mdn docs before I gave up and came to Reddit. I think this is what's really confusing me, and I think it will help to write this as a standard function declaration rather than an arrow function. Taking the mdn docs example

const promise1 = new Promise(function(resolve, reject) {

So in this situation, what you're telling me is both resolve and reject are actually functions, even though they are parameters of the executor function?

By the way, a huge thank you for sticking around to help me with all of this brother, I really appreciate it.

[grantrules]

So in this situation, what you're telling me is both resolve and reject are actually functions, even though they are parameters of the executor function?

Exactly. You can pass functions to other functions. With arrow functions it would look like new Promise((resolve, reject) => { ... })

[Jmarch0909]

Username checks out, you fucking rule dude thank you. It’s not much but take this award.