The operators listed here emit only some of the items emitted on the source observables, based on their criteria. Some of them have already been covered in the previous chapters. They are the following:
| Operator | Description | Chapter |
| debounce | Maps each item to another value | 8 |
| distinct_until_changed | Emits an item only when it is different from the previously emitted item | 8 |
| filter | Emits only items that meet a certain criterion | 6 |
| skip | Skips items some amount of items | 6 |
| take | Emits only some amount of items | 8 |