easy3-5 min58% solve rate

The Event Listener Memory Leak

This WebSocket handler looks clean but will slowly consume all your memory.

Node.jsMemory

The Code

This code passed code review and works in development. But it has a bug that will cause problems in production.

websocket.js

1const WebSocket = require('ws');
2const EventEmitter = require('events');
3 
4const notifications = new EventEmitter();
5 
6const wss = new WebSocket.Server({ port: 8080 });
7 
8wss.on('connection', (ws) => {
9  console.log('Client connected');
10 
11  // Listen for notifications
12  const handler = (data) => {
13    ws.send(JSON.stringify(data));
14  };
15 
16  notifications.on('new-notification', handler);
17 
18  ws.on('message', (message) => {
19    console.log('Received:', message);
20  });
21 
22  ws.on('close', () => {
23    console.log('Client disconnected');
24  });
25});
26 
27// This WebSocket server has a memory leak.
28// It will grow unbounded over time.
29// What's missing?

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