ReplaySubject

"Replays" or emits old values to new subscribers

Examples

Example 1: simple ReplaySubject

( Stackblitz )

// RxJS v6+
import { ReplaySubject } from 'rxjs';

const sub = new ReplaySubject(3);

sub.next(1);
sub.next(2);
sub.subscribe(console.log); // OUTPUT => 1,2
sub.next(3); // OUTPUT => 3
sub.next(4); // OUTPUT => 4
sub.subscribe(console.log); // OUTPUT => 2,3,4 (log of last 3 values from new subscriber)
sub.next(5); // OUTPUT => 5,5 (log from both subscribers)

Additional Resources

• ReplaySubject 📰 - Official docs

• ReplaySubject - In Depth Dev Reference

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📁 Source Code: https://github.com/ReactiveX/rxjs/blob/master/src/internal/ReplaySubject.ts