generator_and_promise.js

const fs = require('fs');

function check_result() {
    return fs.existsSync('foo.txt');
}

function* infiniteSequence() {
    let num = 1
    while (true) {
        yield num
        num = num * 2
    }
}

function sleep(ms) {
    return new Promise(resolve => setTimeout(resolve => {
        resolve(fs.existsSync("foo.txt"))
    }, ms));
}

async function delayedChecking() {
    let res = check_result();
    console.log(`result is ${res}`)
    while (!res) {
        let z = x.next().value;
        console.log(`check ${z} milliseconds later`)
        await sleep(z);
        res = check_result()
    }
}

let x = infiniteSequence()
delayedChecking();

const fs = require('fs');

function check_result() {
    return fs.existsSync('foo.txt');
}

function* infiniteSequence() {
    let num = 1
    while (true) {
        yield num
        num = num * 2
    }
}

function sleepAndCheck(ms) {
    return new Promise((resolve, rejected) =>
        setTimeout(() => {
            resolve(check_result())
        }, ms)
    );
}

async function delayedChecking() {
    let res = check_result();
    console.log(`result is ${res}`)
    while (!res) {
        let z = x.next().value;
        console.log(`check ${z} milliseconds later`)
        res = await sleepAndCheck(z);
        console.log(`result is ${res}`)
    }
}

let x = infiniteSequence()
delayedChecking();