Method onUrlChange

packages/common/src/location/location.ts:232–248

* Registers a URL change listener. Use to catch updates performed by the Angular * framework that are not detectible through "popstate" or "hashchange" events. * * @param fn The change handler function, which take a URL and a location history state. * @returns A function that, when execu

(fn: (url: string, state: unknown) => void)

   * @returns A function that, when executed, unregisters a URL change listener.
   */
  onUrlChange(fn: (url: string, state: unknown) => void): VoidFunction {
    this._urlChangeListeners.push(fn);

    this._urlChangeSubscription ??= this.subscribe((v) => {
      this._notifyUrlChangeListeners(v.url, v.state);
    });

    return () => {
      const fnIndex = this._urlChangeListeners.indexOf(fn);
      this._urlChangeListeners.splice(fnIndex, 1);

      if (this._urlChangeListeners.length === 0) {
        this._urlChangeSubscription?.unsubscribe();
        this._urlChangeSubscription = null;
      }
    };
  }

  /** @internal */
  _notifyUrlChangeListeners(url: string = '', state: unknown) {