person_v1.js

// Use a Person constructor function that must be called with the `new` keyword.
// Prototype link between instances and Person.prototype is implicitly created by calling the Person function with the `new` keyword.

function Person(firstName, lastName) {
  this.firstName = firstName;
  this.lastName = lastName;
  this.isActive = true;
}

Person.prototype.sayName = function() {
  console.log("My name is " + this.firstName);
};

var person1 = new Person('gob', 'bluth');
person1.sayName();

var person2 = new Person('tobias', 'funke');
person2.sayName();

person_v2.js

// Create a Person prototype object and explicitly make a prototype link to instances with Object.create()
// You must write your own function to initialize instances with default data (here, we call it `build`, but it can be called anything).

var Person = {
  build: function(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.isActive = true;
    return this;
  },
  
  sayName: function() {
    console.log("My name is " + this.firstName);
  }
};

var person1 = Object.create(Person);
person1.build("gob", "bluth");
person1.sayName();

var person2 = Object.create(Person);
person2.build("lucille", "bluth");
person2.sayName();

// Make your life easier with a factory function.
function personFactory(firstName, lastName) {
  var tmpPerson = Object.create(Person);
  tmpPerson.build(firstName, lastName);
  return tmpPerson;
}

var person3 = personFactory('tobias', 'funke');
person3.sayName();

person_v3.js

// Use the new ES6 `class` keyword. Results in basically the same code as what's in person_v1.js.
// NOTE: This will not work in most browsers. You must "transpile" the code to es6 using Babel https://babeljs.io/

class Person {
  constructor(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.isActive = true;
  }
  
  sayName() {
    console.log("My name is " + this.firstName);
  }
}

var person1 = new Person('gob', 'bluth');
person1.sayName();