I've been troubleshooting a pretty nasty bug where I've eventually realized that it was caused by mutation of a nested object that was passed down the stream of observables and it really surprised me since I was thinking that Observables and their payload are immutable. to understand it better I've reproduced the scenario in the following CodeSandBox (check out the console logs).
is it an expected behavior when working with rxjs observables?
In your code both streams are referencing the same object from of(obj), that's why you observed the unexpected mutation.
To make data immutable, objDownStream1$ needs to return a copy of the obj instead.
const objDownStream1$ = intervalObj$.pipe(
map((obj) => {
return {...obj, nestedObj: { nestedProp: "downStream1Nested" } }
})
);