Classes in JS

classes.js

class Animal {
  constructor(race) {
    this.race = race;
  }
}

class Cat extends Animal {
  constructor(race) {
    super(race);
  }
  say() {
    console.log(this.race + ' says "Meow!"');
  }
}

class Dog extends Animal {
  constructor(race) {
    super(race);
  }
  say() {
    console.log(this.race + ' says "Bark!"');
  }
}

var cat = new Cat('cheshire')
  , dog = new Dog('bulldog')
;

cat.say();
dog.say();

console.log(cat instanceof Cat);
console.log(cat instanceof Dog);
console.log(cat instanceof Animal);
console.log(dog instanceof Animal);