class Signal {
  #value;
  #listeners;
  constructor(value) {
    this.#value = value;
    this.#listeners = [];
  }
  subscribe(listener) {
    this.#listeners.push(listener);
    let initializeListener = true;
    if(this.#value === undefined) initializeListener = false;
    if(this.#value === null) initializeListener = false;
    if(initializeListener) listener(this.#value); // DO NOTHING IF NO VALUE
    return () => this.unsubscribe(listener); /* Return Unsubscribe Funcion */
  }
  unsubscribe(listener) {
    this.#listeners = this.#listeners.filter((l) => l !== listener);
  }
  #notify() {
    this.#listeners.forEach((listener) => listener(this.#value));
  }
  set value(v) {
    if (this.#value == v) return; // DO NOTHING!
    this.#value = v;
    this.#notify();
  }
  get value() {
    return this.#value;
  }
}