How do you implement a custom WebSocket router?

Question

Accepted Answer

**WebSocket router** — route messages to handlers.

```javascript
const { WebSocketServer } = require("ws");

class WebSocketRouter {
    constructor() {
        this.routes = new Map();
        this.middleware = [];
    }

use(middleware) {
        this.middleware.push(middleware);
    }

on(pattern, handler) {
        const regex = new RegExp("^" + pattern.replace(/:(\w+)/g, "(?<$1>[^/]+)") + "$");
        this.routes.set(regex, handler);
    }

async handle(ws, message) {
        const { type, data } = JSON.parse(message);

// Run middleware
        for (const mw of this.middleware) {
            const result = await mw(ws, { type, data });
            if (result === false) return;
        }

// Find matching route
        for (const [regex, handler] of this.routes) {
            const match = type.match(regex);
            if (match) {
                await handler(ws, data, match.groups || {});
                return;
            }
        }

ws.send(JSON.stringify({ error: "Unknown route" }));
    }
}

// Usage
const router = new WebSocketRouter();

// Middleware
router.use((ws, message) => {
    console.log("Received:", message.type);
    return true;
});

// Routes
router.on("chat:message", async (ws, data) => {
    broadcast({ type: "chat:message", user: ws.user, text: data.text });
});

router.on("user:\w+:profile", async (ws, data, params) => {
    const profile = await getProfile(params[0]);
    ws.send(JSON.stringify({ type: "profile", data: profile }));
});

// Server
const wss = new WebSocketServer({ port: 8080 });
wss.on("connection", (ws) => {
    ws.on("message", (msg) => router.handle(ws, msg));
});
```

Node.js: How do you implement a custom WebSocket router?