EventEmitter class in Node.js - Mini Project: Build & Apply

Basic EventEmitter Usage in Node.js

📖 Scenario: You are building a simple notification system in Node.js where different parts of your app can listen for and react to events.

🎯 Goal: Create a Node.js script that uses the EventEmitter class to emit and listen for a custom event called greet. When the event is emitted, a listener should print a greeting message.

📋 What You'll Learn

Create an EventEmitter instance

Define a listener function for the greet event

Emit the greet event with a name parameter

The listener should print a greeting message using the name

💡 Why This Matters

🌍 Real World

EventEmitters are used in Node.js to handle asynchronous events like user actions, data loading, or system signals.

💼 Career

Understanding EventEmitter is essential for backend developers working with Node.js to build responsive and event-driven applications.

1

Import EventEmitter and create an instance

Write a line to import EventEmitter from the events module and create a constant called emitter as a new EventEmitter instance.

Node.js

// Import EventEmitter and create an instance
// Your code here

Need a hint?

Use require('events') to import EventEmitter and then create a new instance with new EventEmitter().

2

Add a listener for the 'greet' event

Add a listener to emitter for the event named 'greet' using emitter.on. The listener should be a function that takes a parameter name.

Node.js

const EventEmitter = require('events');
const emitter = new EventEmitter();

// Add a listener for the 'greet' event
// Your code here

Need a hint?

Use emitter.on('greet', (name) => { ... }) to listen for the greet event.

3

Print a greeting message inside the listener

Inside the listener function for 'greet', write a line to print Hello, {name}! using console.log and the name parameter.

Node.js

const EventEmitter = require('events');
const emitter = new EventEmitter();

emitter.on('greet', (name) => {
  // Print greeting message here
  // Your code here
});

Need a hint?

Use a template string inside console.log to include the name variable.

4

Emit the 'greet' event with a name

Emit the 'greet' event on emitter with the argument 'Alice' to trigger the listener.

Node.js

const EventEmitter = require('events');
const emitter = new EventEmitter();

emitter.on('greet', (name) => {
  console.log(`Hello, ${name}!`);
});

// Emit the 'greet' event with 'Alice'
// Your code here

Need a hint?

Use emitter.emit('greet', 'Alice') to send the event with the name.