[RxJS] Extract common operator logic into standalone function

/* 
 * From
 */
click$.pipe(
  mergeMapTo(throwError({
    status: 400,
    message: 'Server error'
  }).pipe(
      retryWhen(attempts => {
        return attempts.pipe(
          mergeMap((error, i) => {
            const attemptNumber = i + 1;
            if (
              attemptNumber > 3 ||
              [404, 500].find(e => e === error.status)
            ) {
              console.log('Giving up!');
              return throwError(error);
            }
            console.log(
              `Attempt ${attemptNumber}: retrying in ${attemptNumber *
              1000}ms`
            );
            return timer(attemptNumber * 1000);
          })
        );
      }),
      catchError(err => of(err.message))
    )
  )
).subscribe(console.log);

 

To:

export const genericRetryStrategy = ({
  retryAttempts = 3,
  scalingDuration = 1000,
  excludedStatusCodes = []
}: {
  retryAttempts?: number;
  scalingDuration?: number;
  excludedStatusCodes?: number[];
} = {}) => (obs: Observable<any>) => {
  return obs.pipe(
    retryWhen(attempts => {
      return attempts.pipe(
        mergeMap((error, i) => {
          const attemptNumber = i + 1;
          if (
            attemptNumber > retryAttempts ||
            excludedStatusCodes.find(e => e === error.status)
          ) {
            console.log('Giving up!');
            return throwError(error);
          }
          console.log(
            `Attempt ${attemptNumber}: retrying in ${attemptNumber *
            scalingDuration}ms`
          );
          return timer(attemptNumber * scalingDuration);
        })
      );
    })
  );
};

// simulate network request with error
click$.pipe(
  mergeMapTo(throwError({
    status: 500,
    message: 'Server error'
  }).pipe(
    genericRetryStrategy({
      retryAttempts: 4,
      scalingDuration: 2000
    }),
    // you may want different catching strategy depending on page
    catchError(err => of(err.message))
  ))
).subscribe(console.log);