Node.js Events

The EventEmitter pattern.

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Much of Node is event-driven. The EventEmitter class lets objects emit named events that listeners react to.

emitter.on("event", listener): listen.
emitter.once("event", listener): listen once.
emitter.emit("event", data): trigger.

Servers, streams and sockets are all EventEmitters.

Key Takeaways: Node.js Events

Mastering Node.js Events helps you write clean and reliable Node.js code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.

Node.js Events Code Example

Node.js

import { EventEmitter } from "node:events";

class Shop extends EventEmitter {
  order(item) {
    console.log("Order placed:", item);
    this.emit("ordered", item);
  }
}

const shop = new Shop();
shop.on("ordered", item => console.log("📧 Email sent for", item));
shop.on("ordered", item => console.log("📦 Packing", item));

shop.order("Laptop");

Output

Order placed: Laptop
📧 Email sent for Laptop
📦 Packing Laptop

Run this example on your own computer. The "Get Started" lesson shows how to set it up.

Node.js Events Practice Exercises

Check what you learned in “Node.js Events”.

/ 2 solved

Fill in the blank

Trigger an event.

shop.("ordered", item);

✓ Correct! Not quite. Try again.

Multiple choice

Which class lets objects emit named events?

EventEmitter EventTarget Emitter Observer

✓ Correct! Not quite. Try again.

to save your exercise progress.

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Mark it complete to track your progress.

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Node.js Events

💡 Key Takeaways: Node.js Events

Node.js Events Code Example

Node.js Events Practice Exercises

Key Takeaways: Node.js Events