Events vs callbacks decision in Node.js - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an event emitter instance.

Node.js

const EventEmitter = require('events');
const emitter = new [1]();

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

AEmitterEvent

BEmitter

CEvent

DEventEmitter

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong class name like 'Emitter' or 'Event'.

Forgetting to use parentheses to create an instance.

The EventEmitter class is used to create event emitter instances in Node.js.

2fill in blank

medium

Complete the code to add a callback function for the 'data' event.

Node.js

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

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

A()

Bfunction(data)

Cdata

Devent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'function(data)' without arrow syntax here.

Using empty parentheses which means no parameters.

The callback function receives the event data as a parameter. Using data as the parameter name is common and clear.

3fill in blank

hard

Fix the error in the callback usage by completing the code.

Node.js

function fetchData(callback) {
  setTimeout(() => {
    const result = 'Hello';
    callback([1]);
  }, 1000);
}

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

Aresult

Bcallback

CfetchData

DsetTimeout

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the callback function itself instead of data.

Passing unrelated function names.

The callback function should be called with the data result as argument.

4fill in blank

hard

Fill both blanks to emit an event with a message and listen for it.

Node.js

emitter.[1]('message', 'Hi there!');
emitter.[2]('message', msg => {
  console.log(msg);
});

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

Aemit

Bon

Csend

Dlisten

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send' or 'listen' which are not Node.js EventEmitter methods.

Mixing up 'emit' and 'on' methods.

Use emit to send an event and on to listen for it.

5fill in blank

hard

Fill all three blanks to decide between callback and event for async handling.

Node.js

function processData(data, [1]) {
  if (data.length > 5) {
    [2]('error', new Error('Too long'));
  } else {
    [3](null, data);
  }
}

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

Acallback

Bemitter.emit

Demitter.on

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'emitter.on' instead of 'emitter.emit' to send events.

Confusing callback with event emitter methods.

Use a callback function to handle success or error. Use emitter.emit to send an error event.