class Counter {
  #count = 0;
  get value() {
    return this.#count;
  }
  set value(v) {
    if (v < this.#count) throw new RangeError('Cannot decrease');
    this.#count = v;
  }
}

const c = new Counter();
c.value = 5;
let msg;
try {
  c.value = 3;
} catch (e) {
  msg = e.message;
}
c.value = 10;
console.log(msg, c.value);