RxJs Observable: Execute function if empty/filtered

Question

I've got an Observable that listens to some user input from a text box. If the observed string's length is >=3 (filter), it executes some HTTP call (switchMap).

Now I'd like to detect somehow if the user input has been filtered. Reason:

• If the HTTP call has been done, it should show the results.

• If the user input got filtered (== is invalid), it should clear the results.

Here's the code I'd like to have (see: ifFiltered):

this.userInput.valueChanges
    .filter(val => val && val.length >= 3)
    .ifFiltered(() => this.results = [])
    .switchMap(val => getDataViaHTTP())
    .subscribe(val => this.results = val);

I know, I could place that logic within the filter function for this simple example. But what if I have 10 different filters?

Did I miss any method that satisfies my needs?

Thanks in advance!

Answer 1

Either use partition like here RxJS modeling if else control structures with Observables operators

Or instead of filter use map and pipe the object if the former filter condition is true or null otherwise. so you can catch the null where ever you want in your chain with a filter.

Last option call some function in the else part of the filter function