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.action.filter(el => !(el instanceof observer));
    }
}

class Jack
{
    inform(message)
    {
        console.log(`Jack has been informed about: ${message}`);
    }
}

class Max
{
    inform(message)
    {
        console.log(`Max has been informed about: ${message}`);
    }
}

const autoNews = new AutoNews();

autoNews.register(new Jack());
autoNews.register(new Max());

autoNews.setNews('New Tesla price is 40 000');