Event Emitter

class Emitter {
  constructor() {
    this.events = {}; // Store event name and their corresponding callbacks
  }

  // Subscribe to an event with a callback
  subscribe(eventName, callback) {
    if (!this.events[eventName]) {
      this.events[eventName] = []; // If no callbacks for this event, initialize an array
    }

    // Add the callback to the event's array of listeners
    this.events[eventName].push(callback);

    // Return an object that allows unsubscribing
    return {
      release: () => {
        this.events[eventName] = this.events[eventName].filter(
          (cb) => cb !== callback
        );
      },
    };
  }

  // Emit an event, calling all the callbacks with the passed arguments
  emit(eventName, ...args) {
    if (this.events[eventName]) {
      this.events[eventName].forEach((callback) => {
        callback(...args); // Call each subscribed callback with the arguments
      });
    }
  }
}

// Example usage:
const emitter = new Emitter();

// Subscribing to events
const callback1 = (a, b) => console.log('callback1', a, b);
const callback2 = (a, b) => console.log('callback2', a, b);

const sub1 = emitter.subscribe('event1', callback1);
const sub2 = emitter.subscribe('event2', callback2);
const sub3 = emitter.subscribe('event1', callback1); // Same callback1 again for event1

// Emitting events
emitter.emit('event1', 1, 2);  // callback1 will be called twice
emitter.emit('event2', 3, 4);  // callback2 will be called once

// Unsubscribing
sub1.release(); // Unsubscribe callback1 from event1
sub3.release(); // Unsubscribe callback1 from event1 again

// Emitting event1 again (callback1 should not be called anymore)
emitter.emit('event1', 5, 6);  // callback1 will not be called anymore
/*
callback1 1 2
callback1 1 2
callback2 3 4 
 */