classes example

class Grandfather {
  constructor(name, age, job) {
    this.name = name;
    this.age = age;
    this.job = job;
  }

  aboutMe() {
    console.log(`I'm ${this.name}, I'm ${this.age} years old and I'm ${this.job === 'retired' ? '' : 'a '}${this.job}.`);
  }
}

class Father extends Grandfather {
}

class Son extends Father {
}

let grandad = new Grandfather('Jonathan', 80, 'retired');
grandad.aboutMe(); // I'm Jonathan, I'm 80 years old and I'm retired.

let dad = new Father('John', 40, 'coder');
dad.aboutMe(); // I'm John, I'm 40 years old and I'm a coder.

let son = new Son('Johnny', 18, 'student');
son.aboutMe(); // I'm Johnny, I'm 18 years old and I'm a student.

console.log(son instanceof Son); // true
console.log(son instanceof Grandfather); // true
console.log(Father.prototype.isPrototypeOf(Son.prototype)); // true
console.log(Grandfather.prototype.isPrototypeOf(Son.prototype)); // true
console.log(son); // Grandfather { name: 'Johnny', age: 18, job: 'student' }