class Person {
    constructor(name, age){
    this._name = name;
    this._age = age;
  }
  tellMyName(){
    console.log(`I am ${this._name}`);
  }
  tellMyAge(){
    console.log(`I have ${this._age} years old`);
  }
}

const john = new Person ('John', 40);
const mary = new Person ('Mary', 35);
john.tellMyName();
john.tellMyAge();
mary.tellMyName();
mary.tellMyAge();