RXJS operator function to store a stream in localStorage, then replays from localStorage when provided BehaviourSubject is true. This is helpful if you need to replay a complicated set of observable streams after a browser redirect.

rxjs-localstorage-replay.ts

  /**
   * Stores last emitted value in localStorage and replays if usStore$ is set.
   * If usStore$ is truthy then switches stream to use stored value.
   * If usStore$ is undefined then stream will emit as normal.
   * @param storageKey unique key to use in localStorage
   * @param useStore$ controls if the localStorage value is used
   */
  export default function localStorageReplay<T>(storageKey: string, useStore$: BehaviorSubject<boolean>): MonoTypeOperatorFunction<T> {
    return (input$): Observable<T> => {
      // Observable for parsed stored value, fallsback to input stream.
      const storedValue$ = of(localStorage.getItem(`stream-${storageKey}`)).pipe(
        map(str => (str === 'undefined' ? undefined : JSON.parse(str))),
        catchError(() => input$)
      );
      // if useStore is true set then replay localStorage value
      return useStore$.pipe(
        switchMap(useStore =>
          useStore
            ? storedValue$
            : input$.pipe(tap(val => localStorage.setItem(`stream-${storageKey}`, JSON.stringify(val))))
        ),
        shareReplay(1)
      );
    };
  }

Ho can I use it in a real get ?