Blocked Event Loop Resolved by Worker

blocked_event_loop.js

const getFactorial = (value) => {
  let prevTimestamp = Date.now();
  let currentValue = 0;
  let total = 1;

  while (currentValue < value) {
    const now = Date.now();

    if (now - prevTimestamp >= 1000) {
      total *= ++currentValue;
      prevTimestamp = now;
    }
  }

  return total;
};

const originalTimestamp = Date.now();
let prevTimestamp = originalTimestamp;
let iteration = 0;
const ITERATIONS_NUMBER = 8;
const value = 6;

console.log('START');

console.log(`The factorial of ${value} is`, getFactorial(value));

while (iteration < ITERATIONS_NUMBER) {
  const now = Date.now();

  if (now - prevTimestamp >= 1000) {
    console.log(++iteration);
    prevTimestamp = now;
  }
}

console.log('END after', ((Date.now() - originalTimestamp) / 1000).toFixed(1), 'sec.');

worker_based_refactoring.js

const { Worker, isMainThread, parentPort, workerData } = require('worker_threads');

if (isMainThread) {
  const getFactorial = (value) => {
    return new Promise((resolve, reject) => {
      const worker = new Worker(__filename, { workerData: { value } });
      worker.on('message', resolve);
      worker.on('error', reject);
    });
  };

  const originalTimestamp = Date.now();
  let prevTimestamp = originalTimestamp;
  let iteration = 0;
  const ITERATIONS_NUMBER = 8;
  const value = 6;

  console.log('START');

  getFactorial(value).then((res) => console.log(`The factorial of ${value} is`, res));

  while (iteration < ITERATIONS_NUMBER) {
    const now = Date.now();

    if (now - prevTimestamp >= 1000) {
      console.log(++iteration);
      prevTimestamp = now;
    }
  }

  console.log('END after', ((Date.now() - originalTimestamp) / 1000).toFixed(1), 'sec.');
} else {
  const { value } = workerData;

  let prevTimestamp = Date.now();
  let currentValue = 0;
  let total = 1;

  while (currentValue < value) {
    const now = Date.now();

    if (now - prevTimestamp >= 1000) {
      total *= ++currentValue;
      prevTimestamp = now;
    }
  }

  parentPort.postMessage(total);
}