How to share a single Subject source - rxjs

Question

I'm trying to share a Subject source across multiple functions that filter their actions and do appropriate tasks, the ones that are not filtered should fall trough without modifications.
I've tried merging same source but it doesn't really work the way I need it to...
const source = new Subject()
source.next({ type: 'some type', action: {} })
merge(
source,
source.pipe(filter(...), do something),
source.pipe(filter(...), do something),
source.pipe(filter(...), do something),
source.pipe(filter(...), do something),
).subscribe(...)
In this case I get original source + filtered ones.
I'm expecting to be able provide same source to multiple functions that can filter on types and do async behaviours, rest of the types that were not filtered should fall trough. Hope this is clear enough, or otherwise will try to make a better example. Thanks!
example here

Answer 1

Basically you want one source with actions. Subject is fine way to do this.
Then you want to do some processing on each type of action. You can filter and subscribe to each substream.
const add$ = source.pipe(filter(a => a.type === "add")).subscribe(function onAddAction(a) {});
const remove$ = source.pipe(filter(a => a.type === "remove")).subscribe(function onRemove(a) {});
Or you can prepare substreams and then merge to all processed actions again.
const add$ = source.pipe(filter(a => a.type === "add"), tap(onAdd));
const remove$ = source.pipe(filter(a => a.type === "remove"), tap(onRemove));
const processedAction$ = merge(add$, remove$);
processedAction$.subscribe(logAction);
If you need to do some preprocessing on all actions you can use share or shareReplay. toAction will be called only once per each item.
const subject = new Subject();
const action$ = subject.pipe(map(toAction), share());
const add$ = action$.pipe(filter(isAdd));
...
merge(add$, remove$).subscribe(logAction);
And if you have problems splitting:
function not(predicate) {
return function(item, ...args) {
return !predicate(item, ...args);
}
}
function any(...predicates) {
return function(item, ...args) {
return predicates.some(p => p(item, ...args));
}
}
const a = source.pipe(filter(fa), map(doA));
const b = source.pipe(filter(fb), map(doB));
const c = source.pipe(filter(fc), map(doC));
const rest = source.pipe(filter(not(any(fa, fb, fc)));
merge(a, b, c, rest).subscribe(logAction);