How do you implement a custom EventTarget in Node.js?

Question

Accepted Answer

**EventTarget** — W3C standard event system (available in Node.js).

```javascript
class EventBus extends EventTarget {
    constructor() {
        super();
    }

emit(eventName, detail) {
        const event = new CustomEvent(eventName, { detail });
        this.dispatchEvent(event);
    }

on(eventName, handler) {
        this.addEventListener(eventName, handler);
        return () => this.removeEventListener(eventName, handler);
    }
}

// Usage
const bus = new EventBus();

const unsub = bus.on("data", (event) => {
    console.log("Received:", event.detail);
});

bus.emit("data", { value: 42 });
bus.emit("data", { value: 100 });

unsub(); // unsubscribe
```

**Node.js EventEmitter (alternative):**
```javascript
const { EventEmitter } = require("events");

class EventBus extends EventEmitter {
    emit(eventName, detail) {
        super.emit(eventName, { detail });
    }
}
```

Node.js: How do you implement a custom EventTarget in Node.js?