class Person {
  constructor(firstName = undefined, lastName = undefined) {
    this.firstName = firstName;
    this.lastName = lastName;
    if (this.firstName !== undefined) {
      Object.defineProperty(this, 'firstName', {
        value: firstName,
        writable: false,
      });
    }
    if (this.lastName !== undefined) {
      Object.defineProperty(this, 'lastName', {
        value: lastName,
        writable: false,
      });
    }
  }