How do I make an Observable Interval start immediately without a delay?

Question

I want my observable to fire immediately, and again every second. interval will not fire immediately. I found this question which suggested using startWith, which DOES fire immediately, but I then get a duplicate first entry.

  Rx.Observable.interval(1000).take(4).startWith(0).subscribe(onNext); 

https://plnkr.co/edit/Cl5DQ7znJRDe0VTv0Ux5?p=preview

How can I make interval fire immediately, but not duplicate the first entry?

Answer 1

Before RxJs 6:

Observable.timer(0, 1000) will start immediately.

RxJs 6+

import {timer} from 'rxjs/observable/timer'; timer(0, 1000).subscribe(() => { ... }); 

Answer 2

RxJs 6. Note: With this solution, 0 value will be emitted twice (one time immediately by startWith, and one time by interval stream after the first "tick", so if you care about the value emitted, you could consider startWith(-1) instead of startWith(0)

interval(100).pipe(startWith(0)).subscribe(() => { //your code });  

or with timer:

import {timer} from 'rxjs/observable/timer'; timer(0, 100).subscribe(() => {      });