# The EventEmitter Pattern — Node.js Fundamentals: Modules, Async and Servers

Source: https://www.skillbyai.com/en/nodejs/node-eventemitter

> Use the EventEmitter publish-subscribe pattern that powers streams, HTTP servers and much of Node's core.

## emit and on

Create an emitter, subscribe with `on`, fire an event with `emit`.

```javascript
import { EventEmitter } from "node:events";

const orders = new EventEmitter();

orders.on("placed", (item) => {
  console.log(`Order received: ${item}`);
});

orders.emit("placed", "Laptop");
```

Output:

```
Order received: Laptop
```

## A radio station

An `EventEmitter` is like a **radio station**: it broadcasts (`emit`), and any number of listeners can **tune in** (`on`) without the station knowing who they are.

## Core Node runs on it

HTTP servers, streams, and process itself are all `EventEmitter`s under the hood — `request`, `data`, `close` are all events.