Maintain shared observable state using the scan and shareReplay operators

The scan() is very useful in RxJS. It allows you to maintain a running state over time. In this lesson, we'll look at some of the state types scan can hold: transient or single source of truth, and how we can achieve each of them by combining it with the share operators.

We'll also look at the differences between share() / shareReplay(1) / shareReplay({bufferSize: 1, refCount: true}) and how to avoid memory leaks when using them.