var extend = function (obj1, obj2) {
  for (var key in obj2) {
    obj1[key] = obj2[key];
  }
}

const dog = {
  name: 'Scout',
  breed: ['Husky', 'German Shepherd'],
  age: 4,
  happiness: 50,
  hunger: 10,
  energy: 100,
};

var Dog = function (dogObj) {
  extend(this, dogObj);
}

Dog.prototype.feed = function (food) {
  if (dog.hunger - food > 0) {
    dog.hunger -= food;
  } else {
    dog.hunger = 0;
  }
}

Dog.prototype.play = function (time) {
  if (dog.happiness + time < 100) {
    dog.happiness += time;
  } else {
    dog.happiness = 100;
  }
  if (dog.energy - time > 0) {
    dog.energy -= time;
  } else {
    dog.energy = 0;
  }
}


Dog.prototype.nap = function (time) {
  if (dog.energy + time < 100) {
    dog.energy += time;
  } else {
    dog.energy = 100;
  }
}

var myPetScout = new Dog(dog);
console.log(myPetScout);
console.log(myPetScout instanceof Dog);
console.log(myPetScout.feed)