function Animal() {}
function Dog() {}
Dog.prototype = Object.create(Animal.prototype);
const rover = new Dog();
console.log(rover.hasOwnProperty('constructor'));

function Shape() {}
function Circle(radius) {}
Circle.prototype = Object.create(Shape.prototype);
const shape = new Shape();
console.log(shape instanceof Circle);

function Animal() {}
const dog = new Animal();
console.log(dog.constructor === Animal);

var foo = {};
var bar = Object.create(foo);

foo.a = 1;

console.log(bar.a);

function Person() {}

var person = new Person();

console.log(person instanceof Person);
console.log(person instanceof Object);

function X() {}
X.prototype.getValue = function() {
  return this.value;
};

function Y() {
  this.value = 42;
}
Y.prototype = Object.create(X.prototype);
Y.prototype.constructor = Y;

var y = new Y();
console.log(y.getValue());