Receiving results from workers in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to listen for messages from a worker thread.

Node.js

worker.on('[1]', (message) => {
  console.log('Received:', message);
});

Drag options to blanks, or click blank then click option'

Asend

Bdata

Cresult

Dmessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'data' or 'result' instead of 'message' causes no event to fire.

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

2fill in blank

medium

Complete the code to send a message from the main thread to the worker.

Node.js

worker.[1]({ task: 'processData' });

Drag options to blanks, or click blank then click option'

ApostMessage

Bemit

CsendMessage

Dmessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'emit' or 'sendMessage' will cause errors as they are not valid methods.

The postMessage method sends data to the worker thread.

3fill in blank

hard

Fix the error in the code to correctly receive data from the worker.

Node.js

worker.on('message', ([1]) => {
  console.log('Data:', data);
});

Drag options to blanks, or click blank then click option'

Amsg

Bmessage

Cdata

Dresult

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different parameter name than the variable inside causes a ReferenceError.

The parameter name must match the variable used inside the function to avoid reference errors.

4fill in blank

hard

Fill both blanks to correctly handle errors and exit events from a worker.

Node.js

worker.on('[1]', (error) => {
  console.error('Worker error:', error);
});
worker.on('[2]', (code) => {
  console.log('Worker exited with code', code);
});

Drag options to blanks, or click blank then click option'

Aerror

Bexit

Cclose

Ddisconnect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'close' or 'disconnect' instead of 'exit' will not detect worker termination correctly.

The 'error' event handles errors from the worker, and the 'exit' event fires when the worker stops.

5fill in blank

hard

Fill all three blanks to create a map of worker IDs to their last received messages.

Node.js

const results = {};
workers.forEach(worker => {
  worker.on('[1]', (message) => {
    results[worker.[2]] = message;
  });
});
console.log(results[[3]]);

Drag options to blanks, or click blank then click option'

Amessage

BthreadId

Cworker.threadId

DworkerId

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'workerId' which does not exist, or 'worker.threadId' inside bracket notation incorrectly.

The 'message' event receives data. Each worker has a 'threadId' property used as a key. To access a specific worker's result, use its threadId.