❗️Что будет на выходе:

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

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

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

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

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

const animal = new Animal('Rover');
const dog = new Dog('Rex');

console.log(dog instanceof Animal, dog.speak(), animal.speak(), Dog.prototype.isPrototypeOf(dog));

Ответ: true 'Rex barks.' 'Rover makes a noise.' true

JavaScript test | #JavaScript