如何映射两个 rxjs 流？

Question

I have two async streams:

users = new Subject<User[]>();
groups$ = new Subject<Rights>();
mapped$ = new Subject();

I want to map first stream with value from the second. Using imperative way I do this like:

users.foreach((user: User => {
    user.value = groups.find((g) => g.user == user.id)?.value
});
 

How to do that using RXJS to get mapped result in mapped$ ?

Answer 1

You can use combineLatest to emit when either users$ or groups$ emits, then map to add the group to each user:

combineLatest([users$, groups$]).pipe(
  map(([users, groups]) => users.map(user => {
    user.value = groups.find(g => g.user == user.id)?.value
    return user
  }))
)