prototype.js

/**************************************************************************
 *
 *  🐖🐂🐄🐓 George Orwell explaining Javascript Prototype 🐖🐂🐄🐓
 *
 **************************************************************************/

function Animal(name, type) {
  this.name = name;
  this.type = type;
}

Animal.prototype.isAllowedToWalkOn2Legs = false;
Animal.prototype.isAllowedToSleepInBeds = false;

var napoleon = new Animal("Napoleón", "🐖");
const boxer = new Animal("Boxer", "🐴");

console.log(napoleon.isAllowedToWalkOn2Legs); // false
console.log(boxer.isAllowedToWalkOn2Legs); // false

console.log(Object.getPrototypeOf(napoleon) === Object.getPrototypeOf(boxer)); // true
console.log(Object.getPrototypeOf(napoleon) === Animal.prototype); // true

// Some time later ✊🏼🐖✊🏼

const empoweredPigPrototype = {
  isAllowedToWalkOn2Legs: true,
  isAllowedToCreateNewLaws: false,
  type: "🐖",
  friends: ["🐖", "🐕"]
};

var napoleon = Object.create(empoweredPigPrototype);
const squealer = Object.create(empoweredPigPrototype);

console.log(Object.getOwnPropertyNames(napoleon)); // []

console.log(napoleon.isAllowedToWalkOn2Legs); // true
console.log(squealer.isAllowedToCreateNewLaws); // false

console.log(squealer.friends); // ['🐖', '🐕']
napoleon.friends.push("🐓");
console.log(squealer.friends); // ['🐖', '🐕', '🐓']

napoleon.isAllowedToCreateNewLaws = true;
console.log(napoleon.isAllowedToCreateNewLaws); // true
console.log(squealer.isAllowedToCreateNewLaws); // false