observable_in_action

class Customer {
  checkEmail(news) {
    // here we take a look on news and make a decision buy or not
  }

  findAnotherShop() {
    // search for a new shop for us
  }
  
  checkOrder() {
    // is it okay with my order?
  }

}

const me = new Customer();

const obs = new Observable((customer) => {
  shop.addEventListener('news', (news) => {
    if (news.isSomethingWrong) {
        customer.error(news);
    } else {
        customer.next(news);
    }
  })

  shop.addEventListener('accident', _ => {
    customer.comptele(); // shop is closing
  })


  return () => {
    showToast(`${shop.name} has lost 1 customer. We need do something!`);
  };

});

const  subscription = obs.subscribe({
  next: (news) => me.checkEmail(news),
  error: () => me.checkOrder(),
  complete: () => me.findAnotherShop()
});

subscription.unsubscribe(); 
// it calls "showToast" method
// and when the shop will be closed and we don't get any notifications 
// because Subscriber is stopped when we had unsubscribed