📄 Custom RxJS operators 2/7: "filterNil operator"

#angular #rxjs #filterNil

It is quite common to filter out null and undefined values from the resulting stream. Obviously, the built-in filter operator is the right tool to do the job, however in order to ensure proper type narrowing, the predicate function has to be a user-defined type guard. Therefore, it makes sense to encapsulate it into a custom RxJS operator.

operator

import { filter, OperatorFunction } from 'rxjs';

function filterNil<T>(): OperatorFunction<T, NonNullable<T>> {
  return filter((v): v is NonNullable<T> => v != undefined);
}