'of' vs 'from' operator

Question

Is the only difference between Observable.of and Observable.from the arguments format? Like the Function.prototype.call and Func

Answer 1

Another interesting fact is Observable.of([]) will be an empty array when you subscribe to it. Where as when you subscribe to Observable.from([]) you wont get any value.

This is important when you do a consecutive operation with switchmap.

Ex: In the below example, I am saving a job and then sites, and then comments as a stream.

.do((data) => {
            this.jobService.save$.next(this.job.id);
        })
        .switchMap(() => this.jobService.addSites(this.job.id, this.sites)
            .flatMap((data) => {
                if (data.length > 0) {
                    // get observables for saving
                    return Observable.forkJoin(jobSiteObservables);
                } else {
                    **return Observable.of([]);**
                }
            })).do((result) => {
            // ..
        })
        .switchMap(() => this.saveComments())
....

if there's no site to save, ie; data.length = 0 in addSite section, the above code is returning Observable.of([]) and then goes to save comments. But if you replace it with Observable.from([]), the succeeding methods will not get called.

rxfiddle