Node.js: How do you implement a WebSocket chat room with presence tracking?

1const { WebSocketServer } = require("ws");
2
3class ChatRoom {
4    constructor() {
5        this.rooms = new Map();
6    }
7
8    join(roomId, ws, user) {
9        if (!this.rooms.has(roomId)) {
10            this.rooms.set(roomId, new Map());
11        }
12        this.rooms.get(roomId).set(ws, user);
13        this.broadcast(roomId, {
14            type: "user:joined",
15            user,
16            users: this.getUsers(roomId),
17        });
18    }
19
20    leave(roomId, ws) {
21        const room = this.rooms.get(roomId);
22        if (room) {
23            const user = room.get(ws);
24            room.delete(ws);
25            this.broadcast(roomId, {
26                type: "user:left",
27                user,
28                users: this.getUsers(roomId),
29            });
30        }
31    }
32
33    message(roomId, ws, text) {
34        const user = this.rooms.get(roomId)?.get(ws);
35        if (user) {
36            this.broadcast(roomId, {
37                type: "message",
38                user,
39                text,
40                timestamp: Date.now(),
41            });
42        }
43    }
44
45    getUsers(roomId) {
46        const room = this.rooms.get(roomId);
47        return room ? Array.from(room.values()) : [];
48    }
49
50    broadcast(roomId, data) {
51        const room = this.rooms.get(roomId);
52        if (!room) return;
53        const msg = JSON.stringify(data);
54        room.forEach((_, ws) => {
55            if (ws.readyState === 1) ws.send(msg);
56        });
57    }
58}