14. Event Emitter

In modern application development, the asynchronous event-driven architecture plays a crucial role, especially in handling operations where the response time is uncertain. This architecture allows for a decoupled system where objects (emitters) can emit events at any time, and function objects (listeners) respond to these events as they are triggered.

The challenge here is to implement an EventEmitter class that encapsulates this behavior. The class should provide mechanisms to:

• Emit events: Trigger an event by name, executing all callbacks subscribed to this event.
• Subscribe to events: Allow functions to listen for specific events and respond when those events are emitted. Each subscription should provide a way to release (unsubscribe) itself to avoid memory leaks and unintended behavior.

The EventEmitter class should work as follows:

class EventEmitter {
  constructor() {
    this.events = {};
  }

  subscribe(eventName, callback) {
    // Logic to add a listener for the event
  }

  emit(eventName, ...args) {
    // Logic to trigger an event and call all subscribed listeners
  }
}

With this setup, you can create an instance of EventEmitter, subscribe functions to listen for named events, and emit those events at any point in your application. This approach is fundamental in creating non-blocking, asynchronous flows and is at the heart of many JavaScript frameworks and libraries.

This task will test your ability to work with higher-order functions, callbacks, and the principles of event-driven programming. Implementing the EventEmitter class will deepen your understanding of these concepts, which are pivotal in modern JavaScript development.