Any reason to use shareReplay(1) in a BehaviorSubject pipe?

Question

I'm using a library that exposes data from a service class using a pretty common BehaviorSubject pattern. The only notable difference with the implementation and what I have seen/used myself is the addition of a pipe with a shareReplay(1) operator. I'm not sure if the shareReplay is required. What effect, if any, does the shareReplay have in this case?

// "rxjs": "^6.3.0"
this.data = new BehaviorSubject({});
this.data$ = this.data.asObservable().pipe(
   shareReplay(1) 
)

Note: I've read a number of articles on shareReplay, and I've seen questions about different combinations of shareReplay and Subject, but not this particular one

Answer 1

Not in your example but imagine if there was some complex logic in a map function that transformed the data then the share replay would save that complex logic being run for each subscription.

const { BehaviorSubject } = rxjs;
const { map, shareReplay } = rxjs.operators;

const bs$ = new BehaviorSubject('initial value');

const obs$ = bs$.pipe(
  map(val => {
    console.log('mapping');
    return 'mapped value';
  }),
  shareReplay({bufferSize:1, refCount: true})
);

obs$.subscribe(val => { console.log(val); });

obs$.subscribe(val => { console.log(val); });

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Compare without the share, the map happens twice.

const { BehaviorSubject } = rxjs;
const { map } = rxjs.operators;

const bs$ = new BehaviorSubject('initial value');

const obs$ = bs$.pipe(
  map(val => {
    console.log('mapping');
    return 'mapped value';
  })
);

obs$.subscribe(val => { console.log(val); });

obs$.subscribe(val => { console.log(val); });

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