var CreatePerson = function(firstName) {

​

  // revealing pattern

  return {

    walk: walk,

    sayHello: sayHello

  };

  function walk () {

    console.log("I am walking!");    

  }

  function sayHello () {

    console.log("Hello, I'm " + firstName);

  }

};

​

// testing the factory

var girl = CreatePerson("Jane");

girl.walk();

girl.sayHello();

​

​

var CreateStudent = function(firstName, subject) {

  var person = CreatePerson(firstName);

  var newMethods = {

   sayHello: function(){

      console.log("Hello, I'm " + firstName + ". I'm studying " + subject + "."); 

   },

    sayGoodBye: function() {

      console.log("Goodbye!");

    }    

  };

  // start with {} so person is not mutated

  var student = Object.assign({}, person, newMethods);

  return Object.create(student);

};

​

// testing the factory

var student = CreateStudent("Janet", "Applied Physics");

student.sayHello();

student.sayGoodBye();

​

​

​