class Base {
  static count = 0;
  static #secret;
  static {
    Base.#secret = 10;
    Base.count += 1;
  }
  static getSecret() {
    return Base.#secret;
  }
}

class Derived extends Base {
  static {
    Base.count += 100;
  }
}

console.log(Base.count, Derived.count, Base.getSecret());