Event Relay Pattern

1. Introduction

The Event Relay Pattern is a design pattern used in software architecture that facilitates communication between components in a loosely coupled way. It allows for events to be broadcasted to multiple listeners without the components needing to know about each other directly.

2. Key Concepts

• **Events:** These are notifications that something has happened within the system.
• **Publishers:** Components that generate events and publish them.
• **Subscribers:** Components that listen for events and react to them accordingly.
• **Event Bus:** A common medium through which events are published and subscribed to.

3. Implementation

Here’s a simple example of implementing the Event Relay Pattern in JavaScript:

class EventBus {
    constructor() {
        this.listeners = {};
    }
    
    subscribe(event, fn) {
        if (!this.listeners[event]) {
            this.listeners[event] = [];
        }
        this.listeners[event].push(fn);
    }
    
    publish(event, data) {
        if (this.listeners[event]) {
            this.listeners[event].forEach(fn => fn(data));
        }
    }
}

// Usage
const bus = new EventBus();

bus.subscribe('dataReceived', (data) => {
    console.log('Data received:', data);
});

bus.publish('dataReceived', { id: 1, name: 'Item 1' });
            

4. Best Practices

• Keep your event names descriptive and consistent.
• Limit the number of subscribers to prevent performance issues.
• Use a central Event Bus for easy management of events.
• Consider using a library or framework that supports the Event Relay Pattern.

5. FAQ