Javascript Observer Pattern

index.js

const observer = new Observer();

const unsubscribe = observer.subscribe(a => console.log(a));

observer.broadcast('1');

unsubscribe();

observer.broadcast('1');

Observer.js

class Observer {
  constructor() {
    this.observers = [];
  }
  
  subscribe(fn) {
    this.observers.push(fn);
   
    return () => this.observers = this.observers.filter(subscriber => subscriber !== fn);
  }
  
  broadcast(data) {
    this.observers.forEach(subscriber => subscriber(data));
   
    return data;
  }
}