The RxJS documentation has a excellent feature called Operator Decision Tree which makes choosing an operator easier.

Starting at the RxJS home page, select API docs and then the Operator Decision Tree. By responding to each question asked about what you are trying to achieve you will be guided to the appropriate operator.

The animated GIF demonstrates how the Operator Decision Tree identified that I should use the map operator to apply a function to each emitted value.

Acknowledgments

Many thanks to Deborah Kurata and her excellent RxJS in Angular: Reactive Development Pluralsight course for making me aware of this feature.