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

Animal.prototype.speak = function () {
  return `${this.name} makes a sound.`;
};

function Dog(name, breed) {
  Animal.call(this, name);
  this.breed = breed;
}

Dog.prototype = Object.create(Animal.prototype);
Dog.prototype.constructor = Dog;

Dog.prototype.speak = function () {
  return `${this.name} barks!`;
};

const dog = new Dog("Rex", "Labrador");

console.log(dog.speak());
console.log(dog instanceof Dog);
console.log(dog instanceof Animal);
console.log(Object.getPrototypeOf(dog) === Animal.prototype);