UsamaAshraf

const myEmitter = require('./my_emitter');

// Perform the registration steps

// Pass the new user object as the message passed through by this event.
myEmitter.emit('user-registered', user);

UsamaAshraf

const myEmitter = require('./my_emitter');

myEmitter.on('user-registered', (user) => {
  // Send an email or whatever.
});

UsamaAshraf

const myEmitter = require('./my_emitter');
const sendEmailOnRegistration = require('./send_email_on_registration');
const someOtherListener = require('./some_other_listener');


myEmitter.on('user-registered', sendEmailOnRegistration);
myEmitter.on('user-registered', someOtherListener);

UsamaAshraf

module.exports = (user) => {
  // Send a welcome email or whatever.
}

UsamaAshraf

const myEmitter = require('./my_emitter');

// Perform the registration steps

// The application should react differently if the new user has been activated instantly.
if (user.activated) {
  myEmitter.emit('user-registered:activated', user);
  
} else {
  myEmitter.emit('user-registered', user);

UsamaAshraf

const myEmitter = require('./my_emitter');
const sendEmailOnRegistration = require('./send_email_on_registration');
const someOtherListener = require('./some_other_listener');
const doSomethingEntirelyDifferent = require('./do_something_entirely_different');


myEmitter.on('user-registered', sendEmailOnRegistration);
myEmitter.on('user-registered', someOtherListener);

myEmitter.on('user-registered:activated', doSomethingEntirelyDifferent);

UsamaAshraf

class ChatUser {
  
  displayNewMessageNotification(newMessage) {
    // Push an alert message or something.
  }
  
  // `chatroom` is an instance of EventEmitter.
  connectToChatroom(chatroom) {
    chatroom.on('message-received', this.displayNewMessageNotification);
  }

UsamaAshraf

module.exports = (user) => {
  setImmediate(() => {
    // Send a welcome email or whatever.
  });
}

UsamaAshraf

class PostsController < ApplicationController  
  def index    
    posts = Post.all     
     
    render json: posts  
  end
end

class Post
  belongs_to :author, class_name: 'User'

UsamaAshraf

class PostsController < ApplicationController  
  def index    
    # Runs a SQL join with the users table.
    posts = Post.includes(:author).all     
     
    render json: posts  
  end
end