Is it OK to use filter() instead of ofType()

Question

In @ngrx/effects we have an operator called ofType. We use this operator in our effects to filter a specific action. For example in the following effect I used this operator to run a request just after login action:

    @Effect()
    login = this.actions.pipe(
        ofType(UserActions.LOGIN_START),
        switchMap((action: Action) => {
        console.log("login effect")
        return this.http.post()
        ...
        })
    )

ofType() is from @ngrx/effects. I replaced it with filter() and it seems to work properly. Are the exactly the same?

    @Effect()
    login = this.actions.pipe(
        filter(action => action.type == UserActions.LOGIN_START),
        switchMap((action: Action) => {
        console.log("login effect")
        return this.http.post()
        ...
        })
    )

Is anything wrong if I use filter() instead of ofType()?

Answer 1

Yes and no. They both work, but the advantage of using ofType is that the action is typed in the rest of the stream.

actions$.pipe(
  filter(action => action.type === 'LOGIN_START'),
  someMap(action) => {
    // action is inferred to Action
  })

VS

actions$.pipe(
  ofType(logingStart),
  someMap(action) => {
    // action is inferred to logingStart
  })

Answer 2

I think, it's OK, since the ofType operator uses the RxJS filter operator under the hood, and supports using both string and ActionCreator actions, like the following:

export function ofType(
  ...allowedTypes: Array<string | ActionCreator<string, Creator>>
): OperatorFunction<Action, Action> {
  return filter((action: Action) =>
    allowedTypes.some((typeOrActionCreator) => {
      if (typeof typeOrActionCreator === 'string') {
        // Comparing the string to type
        return typeOrActionCreator === action.type;
      }

      // We are filtering by ActionCreator
      return typeOrActionCreator.type === action.type;
    })
  );
}

https://github.com/ngrx/platform/blob/master/modules/effects/src/actions.ts#L133