System Design Quiz Practice

class SharedBus {
  constructor() { this.subs = []; }
  subscribe(s) { this.subs.push(s); }
  publish(msg) { for (const s of this.subs) s.handleBusMessage(msg); }
}
class Server {
  constructor(name, bus) { this.name = name; this.conns = new Map(); bus.subscribe(this); }
  connect(id) { this.conns.set(id, true); }
  send(to, text) { console.log(`from ${this.name}`); this.bus?.publish({ to, text }); }
  handleBusMessage({ to, text }) {
    if (this.conns.has(to)) console.log(`${this.name}: delivering "${text}" to ${to}`);
  }
}
const bus = new SharedBus();
const s1 = new Server("Server1", bus); s1.bus = bus;
const s2 = new Server("Server2", bus); s2.bus = bus;
s1.connect("userA"); s2.connect("userB");
s1.send("userB", "hi");