app.js

import * as MainController from './MainController';

MainController.addBook('Harry Potter');
MainController.addBook('Crazy ducks');
MainController.addBook('Zombie land');
console.log(MainController.myBooks());

BooksController.js

// Private variable
var books = [];

// Private functions
// Sort the books in alphabetical order
function sortBooks() {
  return books.sort((a, b) => (a > b ? 1 : -1));
}

// Public functions
export function getBooks() {
  var sortedBooks = sortBooks();
  return sortedBooks;
}

export function addBooks(book) {
  books.push(book);
}

MainController.js

import * as BooksCtrl from './BooksController';

// Public functions
export function addBook(book) {
  BooksCtrl.addBooks(book);
  console.log(`Book ${book} added.`);
}

export function myBooks() {
  return BooksCtrl.getBooks();
}

module-pattern-es5.js

var BooksController = (function() {
  // Private variable

  var books = [];

  // Private functions
  // Sort the books in alphabetical order
  function sortBooks() {
    return books.sort((a, b) => (a > b ? 1 : -1));
  }

  // Public functions
  return {
    getBooks: function() {
      var sortedBooks = sortBooks();
      return sortedBooks;
    },

    addBooks: function(book) {
      books.push(book);
    },
  };
})();

var MainController = (function(BooksCtrl) {
  // Public functions
  return {
    addBook: function(book) {
      BooksCtrl.addBooks(book);
      console.log(`Book ${book} added.`);
    },

    myBooks: function() {
      return BooksCtrl.getBooks();
    },
  };
})(BooksController);

console.log(BooksController);

MainController.addBook('Harry Potter');
MainController.addBook('Crazy ducks');
MainController.addBook('Zombie land');
console.log(MainController.myBooks());