empty
Example 1: empty immediately completes
// RxJS v6+
import { empty } from 'rxjs';
//output: 'Complete!'
const subscribe = empty().subscribe({
next: () => console.log('Next'),
complete: () => console.log('Complete!')
});
Example 2: empty with timer
// RxJS v6+
import { interval, fromEvent, merge, empty } from 'rxjs';
import { switchMap, scan, takeWhile, startWith, mapTo } from 'rxjs/operators';
const countdownSeconds = 10;
const setHTML = id => val => (document.getElementById(id).innerHTML = val);
const pauseButton = document.getElementById('pause');
const resumeButton = document.getElementById('resume');
const interval$ = interval(1000).pipe(mapTo(-1));
const pause$ = fromEvent(pauseButton, 'click').pipe(mapTo(false));
const resume$ = fromEvent(resumeButton, 'click').pipe(mapTo(true));
const timer$ = merge(pause$, resume$)
.pipe(
startWith(true),
// if timer is paused return empty observable
switchMap(val => (val ? interval$ : empty())),
scan((acc, curr) => (curr ? curr + acc : acc), countdownSeconds),
takeWhile(v => v >= 0)
)
.subscribe(setHTML('remaining'));
- 🎥 💵 - André Staltz
Last modified 2yr ago