Can you explain what Worker Threads in Node.js are and how they are used for multithreading?

In Node.js, Worker Threads is a module that allows creating separate threads to execute JavaScript code in parallel with the main thread. By default, Node.js operates in a single-threaded mode, which is good for I/O but inefficient for CPU-intensive tasks.

Worker Threads create full-fledged threads that can perform computations without blocking the main event loop. They communicate with the main thread via messages (postMessage and on('message')).

Example usage:

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

if (isMainThread) {
  const worker = new Worker(__filename);
  worker.on('message', msg => console.log('From worker:', msg));
  worker.postMessage('Hello, worker!');
} else {
  parentPort.on('message', msg => {
    parentPort.postMessage(`Received: ${msg}`);
  });
}

Thus, Worker Threads enable efficient parallelization of tasks in Node.js, improving performance for computations.