nodejs concurrency

let number = 0;
let temp;

const inc = () => new Promise(resolve => {
    setTimeout(() => {
        temp = number;
        number = temp + 1;
        resolve();
    }, 4000)
});

const concurrency = 100;

const pool = new Array(concurrency);

for(let i = 0; i < concurrency; i++) {
    pool[i] = inc();
}

Promise.all(pool).then(() => {
    console.log(number);
});
// prints concurrency value

with sleep

let number = 0;
//let temp;
const sleep = (seconds) => {
    return new Promise((resolve) => {
      setTimeout(() => {
        resolve();
      }, seconds * 1000);
    });
  };



const inc = async () => {
    let temp = number;
    await sleep(0);
    number = temp + 1;
}

const concurrency = 100;

const pool = new Array(concurrency);

for(let i = 0; i < concurrency; i++) {
    pool[i] = inc();
}

Promise.all(pool).then(() => {
    console.log(number);
});
// prints 1