Receiving results from workers in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main way to receive results from worker threads in Node.js?

You listen for the 'message' event on the worker instance to receive data sent back from the worker thread.

beginner

How do you send data from a worker thread back to the main thread?

Use the worker's parentPort.postMessage() method inside the worker to send data back to the main thread.

intermediate

Why is it important to handle errors when receiving results from workers?

Because workers run in separate threads, errors can happen independently. Handling errors prevents crashes and helps debug issues.

beginner

What Node.js module do you use to create worker threads?

You use the 'worker_threads' module to create and manage worker threads.

intermediate

How can you ensure the main thread waits for a worker's result before continuing?

You can wrap the worker's message event in a Promise and await it, so the main thread pauses until the worker sends its result.

Which event do you listen to on a worker to get results?

A data

B response

C result

D message

The 'message' event is emitted when the worker sends data back to the main thread.

How do you send data from the main thread to a worker?

A worker.emit()

B worker.send()

C worker.postMessage()

D worker.write()

The main thread uses worker.postMessage() to send data to the worker.

Which module must you import to use worker threads?

A worker_threads

B cluster

C child_process

D events

The 'worker_threads' module provides the Worker class for threading.

What method inside a worker sends messages back to the main thread?

A parentPort.send()

B parentPort.postMessage()

C process.send()

D worker.postMessage()

Inside a worker, parentPort.postMessage() sends data back to the main thread.

How can you handle worker results asynchronously in the main thread?

A Wrap the message event in a Promise and await it

B Use setTimeout to wait for results

C Call worker.wait() method

D Use synchronous blocking calls

Wrapping the message event in a Promise lets you await the worker's result cleanly.

Explain how the main thread receives and handles results from a worker thread in Node.js.

Think about events and message passing between threads.

Describe how you can make the main thread wait for a worker's result before continuing execution.

Consider how async code can pause until data arrives.