pubsub.js

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

  subscription (eventName, func) {
    return {
      subscribe: () => {
        if (this.events[eventName]) {
          this.events[eventName].push(func);
          console.log(`${func.name} has subscribed to ${eventName} Topic!`)
        } else {
          this.events[eventName] = [func];
          console.log(`${func.name} has subscribed to ${eventName} Topic!`)
        }
      },

      unsubscribe: () => {
        if(this.events[eventName]){
          this.events[eventName] = this.events[eventName].filter((subscriber) => subscriber !== func);
          console.log(`${func.name} has unsubscribed from ${eventName} Topic!`)
        }
      }


    }
  } 


  publish(eventName, ...args) {
    const funcs = this.events[eventName];
    if (Array.isArray(funcs)) {
      funcs.forEach((func) => {
        func.apply(null, args);
      });
    }
  }
}

const speak = (param) => {
  console.log(`I am ${param}`);
};

const greetAll = (x, y, z) => {
  console.log(`Hello ${x}, ${y}, ${z}`);
};

const pubsub = new Pubsub();


pubsub.subscription("greet", greetAll).subscribe() // prints greetAll has subscribed to greet Topic!

pubsub.subscription("sayName", speak).subscribe() // prints speak has subscribed to sayName Topic!
pubsub.subscription("sayName", greetAll).unsubscribe() // prints greetAll has unsubscribed from sayName Topic!



pubsub.publish("greet", "Lawrence Eagles", "John Doe", "Jane Doe"); // prints Hello Lawrence Eagles, John Doe, Jane Doe

pubsub.publish("sayName", "Lawrence Eagles"); // prints I am Lawrence Eagles