Polymorphe Ereignis-Emitter-Hierarchie für abstrakte React-Zustands-Controller

class AbstractStateController {
  #listeners = new Map();
  constructor(initialState) {
    if (new.target === AbstractStateController) {
      throw new TypeError("Cannot instantiate abstract class directly.");
    }
    this.state = Object.freeze({ ...initialState });
  }
  subscribe(event, handler) {
    if (!this.#listeners.has(event)) this.#listeners.set(event, new Set());
    this.#listeners.get(event).add(handler);
    return () => this.#listeners.get(event).delete(handler);
  }
  emit(event, payload) {
    this.#listeners.get(event)?.forEach((fn) => fn(payload, this.state));
  }
}