observer.js

class AutoNews {
	constructor() {
		this.news = '';
		this.actions = [];
	}
	setNews(text) {
		this.news = text;
		this.notifyAll();
	}
	notifyAll() {
		return this.actions.forEach((subs) => subs.inform(this));
	}
	register(observer) {
		this.actions.push(observer);
	}
	unregister(observer) {
		this.actions = this.actions.filter((el) => !(el instanceof observer));
	}
}
class Jack {
	inform(message) {
		console.log(`Jack has been informed about : ${message.news}`);
	}
}
class Max {
	inform(message) {
		console.log(`Max has been informed about : ${message.news}`);
	}
}
var autoNews = new AutoNews();
autoNews.register(new Jack());
autoNews.register(new Max());
autoNews.setNews('BTC PRICE IS 45 000')