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

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

function Shape() {}

function Circle(radius) {
  this.radius = radius;
}

Circle.prototype = Object.create(Shape.prototype);
Circle.prototype.constructor = Circle;

const shape = new Shape();
const circle = new Circle(5);

console.log(circle instanceof Circle);
console.log(circle instanceof Shape);
console.log(shape instanceof Circle);
console.log(shape instanceof Shape);

var x = 1;
function changeX() { x = 2; }
changeX();
console.log(x);

console.log(typeof null);

const string = "hello world";
const result = string.replace(/l/g, "");
console.log(result);

const obj = { a: 1, b: 2, c: 3 };
let result = "";
for (const [key, value] of Object.entries(obj)) {
  result += key + value;
}
console.log(result);

const array = [
  { name: 'John', score: 80 },
  { name: 'Jane', score: 95 },
  { name: 'Doe', score: 88 },
];

const result = array.every(obj => obj.score >= 80);

console.log(result);

const a = [1, 2, 3];
const b = a.slice(0, 2).push(4);
console.log(b);

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());

function Animal(){ 
  this.type = "animal"
}
   
function Dog(){ 
  this.name = "dog"
}
 
Dog.prototype = new Animal()
 
var PavlovPet = new Dog(); 
 
console.log(PavlovPet.__proto__ === Dog.prototype)
console.log(Dog.prototype.__proto__ === Animal.prototype)

function getArr() {
  return Array.from(arguments);
}

const result = getArr(...[1, 2, 3]);

console.log(result);

function* gen() {
  yield *[1,1];
  yield 2;
  yield 3;
}

const generator = gen();

console.log(generator.next().value);
console.log(generator.next().value);

for (const value of generator) {
  console.log(value);
}

function A() {}
A.prototype.value = 1;

function B() {}
B.prototype = new A();

B.prototype.value = 2;

var b = new B();
console.log(b.value);

console.log([] == []);

let obj = { a: 1 };
let proto = { b: 2 };

Object.setPrototypeOf(obj, proto);

for (let key in obj) {
  console.log(key);
}

const a = [1, 2, 3];
const b = a;

b[0] = 0;

console.log(a);

let obj = { a: 1 };
Object.freeze(obj);

console.log(Object.isFrozen(obj));
console.log(obj.a = 2);
console.log(obj.a);

let x = 10;
let y = 5;

x += y -= x *= y;

console.log(x);

console.log(1 + '2' + '2');