RxJS custom operator to debounce a stream for set time after first value is emitted.

rxjs-debounce-after-first.ts

  /**
   * Debounce after first emit.
   * This operator will debounce all requests apart from the first for a set duration.
   * @param ms time to wait in milliconds.
   */
  const debounceAfterFirst = <T,>(ms: number) => (source: Observable<T>) => {
    return source.pipe(
      map((val: T, index: number) => ({ val, index } as { index: number; val: T })),
      debounce(({ index }) => timer(index === 0 ? 0 : ms)),
      map(({ val }) => val)
    );
  };