RxJS operator functions

operators.ts

import { Observable } from 'rxjs';
import { filter } from 'rxjs/operators';

function inputIsNotNullOrUndefined<T>(input: null | undefined | T): input is T {
  return input !== null && input !== undefined;
}

export function isNotNullOrUndefined<T>() {
  return (source$: Observable<null | undefined | T>) =>
    source$.pipe(
      filter(inputIsNotNullOrUndefined)
    );
}