class Counter {
  #count = 0;
  static #instances = 0;
  constructor() { Counter.#instances++; }
  #increment() { this.#count++; }
  incrementAndGet() {
    this.#increment();
    return this.#count;
  }
  static get total() { return Counter.#instances; }
}

class SpecialCounter extends Counter {
  incrementAndGet() {
    return super.incrementAndGet() * 2;
  }
}

const c1 = new Counter();
const c2 = new SpecialCounter();
console.log(`${c1.incrementAndGet()} ${c2.incrementAndGet()} ${Counter.total}`);