pub-sub.js

// Publisher
class Video {
 constructor(observable, name, content) {
   this.observable = observable;
   this.name = name;
   this.content = content;
   // publish the ‘video-uploaded’ event
   this.observable.publish('video-uploaded', {
     name,
     content,
   });
 }
}
// Subscriber
class User {
 constructor(observable) {
   this.observable = observable;
   this.intrestedVideos = [];
   // subscribe with the event naame and the call back function
   this.observable.subscribe('video-uploaded', this.addVideo.bind(this));
 }
 
 addVideo(video) {
   this.intrestedVideos.push(video);
 }
}
// Observer 
class Observable {
 constructor() {
   this.handlers = [];
 }
 
 subscribe(event, handler) {
   this.handlers[event] = this.handlers[event] || [];
   this.handlers[event].push(handler);
 }
 
 publish(event, eventData) {
   const eventHandlers = this.handlers[event];
 
   if (eventHandlers) {
     for (var i = 0, l = eventHandlers.length; i < l; ++i) {
       eventHandlers[i].call({}, eventData);
     }
   }
 }
}
// usage
const observable = new Observable();
const user = new User(observable);
const video = new Video(observable, 'ES6 Design Patterns', videoFile);