RxJS publishReplay() Multicasting Operator

RxJS publishReplay() operator is a multicasting operator that uses behavior subject, wherein it can buffer the values and replay the same to the new subscribers and returns ConnectableObservable. Here, the connect() method has to be used to subscribe to the observable created.

Syntax:

Following is the syntax of the RxJS publishReplay() multicasting operator:

publishReplay(value); // Here, value is the number of times that it has to replay.

publishReplay<T, R>(bufferSize?: number, windowTime?: number, selectorOrScheduler?: SchedulerLike | OperatorFunction<T, R>, scheduler?: SchedulerLike): UnaryFunction<Observable<T>, ConnectableObservable<R>>

Parameter Explanation

bufferSize: It is an optional. Its default value is undefined. Type: number.
windowTime: It is an optional. Its default value is undefined. Type: number.
selectorOrScheduler: It is an optional. Its default value is undefined. Type: SchedulerLike | OperatorFunction.
scheduler: It is an optional. Its default value is undefined. Type: SchedulerLike.

Return value

The RxJS publishReplay() operator returns a ConnectableObservable.

Let us see an example of the RxJS publishReplay() operator to understand it clearly.

Example

import { interval} from 'rxjs';
import { take, publishReplay} from 'rxjs/operators';
let observer = interval(1000).pipe(
   take(3),
   publishReplay(2)
);
const subscribe_one = observer.subscribe(
   x => console.log("Value from Sub1 = "+x)
);
const subscribe_two = observer.subscribe(
   x => console.log("Value from Sub2 = "+x)
);
observer.connect();
setTimeout(() => {
   const subscribe_three = observer.subscribe(
      x => console.log("Value from Sub3 = "+x)
   );
}, 2000);

Output:

After executing the above example, you will see the following result: