index.js

const { Worker } = require('worker_threads');
const path = require('path');

const arrayCount = 2000000;
const threadCount = 4;
let initialTime = new Date();

for (let i = 0; i < threadCount; i++) {
  const worker = new Worker(path.resolve('./worker.js'));
  worker.on('message', () => {
    const now = new Date();
    console.log(`[worker ${worker.threadId} finish]: ${now - initialTime} ms`);
  });
  worker.postMessage(arrayCount / threadCount);
}