Event Bus and Application Architecture

Implementing a communication system between components using an event bus.

Event Bus Implementation

1class EventBus {
2  constructor() {
3    this.events = {};
4  }
5
6  // Register a listener
7  on(eventName, callback) {
8    if (!this.events[eventName]) {
9      this.events[eventName] = [];
10    }
11    this.events[eventName].push(callback);
12
13    // Return a function to remove the listener
14    return () => this.off(eventName, callback);
15  }
16
17  // Remove a listener
18  off(eventName, callback) {
19    if (this.events[eventName]) {
20      this.events[eventName] = this.events[eventName].filter(cb => cb !== callback);
21    }
22  }
23
24  // One-time listener
25  once(eventName, callback) {
26    const onceCallback = (...args) => {
27      callback(...args);
28      this.off(eventName, onceCallback);
29    };
30    this.on(eventName, onceCallback);
31  }
32
33  // Emit an event
34  emit(eventName, ...args) {
35    if (this.events[eventName]) {
36      this.events[eventName].forEach(callback => {
37        try {
38          callback(...args);
39        } catch (error) {
40          console.error(`Error in event listener for ${eventName}:`, error);
41        }
42      });
43    }
44  }
45
46  // Remove all listeners for an event
47  removeAllListeners(eventName) {
48    if (eventName) {
49      delete this.events[eventName];
50    } else {
51      this.events = {};
52    }
53  }
54}
55
56// Global event bus instance
57const eventBus = new EventBus();
58
59// Usage in different application modules
60// Module A
61eventBus.on('dinosaurEscape', (dinosaurData) => {
62  showEmergencyAlert(dinosaurData);
63});
64
65// Module B
66function handleDinosaurEscape(dinosaur) {
67  eventBus.emit('dinosaurEscape', {
68    id: dinosaur.id,
69    name: dinosaur.name,
70    location: dinosaur.enclosure,
71    dangerLevel: dinosaur.dangerLevel
72  });
73}
74
75// Module C
76eventBus.on('dinosaurEscape', (dinosaurData) => {
77  if (dinosaurData.dangerLevel > 8) {
78    activateEmergencyProtocols();
79  }
80});