class Person {
  constructor(name, age) {
    this._name = name;
    this._age = age;
  }

  tellMyName() {
    return 'I am ' + this._name;
  }

  tellMyAge() {
    return 'I am ' + this._age + ' years old';
  }
}

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

console.log(john.tellMyName());
console.log(john.tellMyAge());

console.log(mary.tellMyName());
console.log(mary.tellMyAge());