observable.js

const createObservable = () => {
  let observers = [];
  
  const subscribe = (observer) => {
    observers.push(observer);
    return () => {
    	observers = observers.filter(o => o !== observer);
    };
  };
  
  const publish = (toPublish) => {
  	observers.forEach(observer => observer(toPublish));
  };
  
  return {subscribe, publish};
};