Do you know "defaultIfEmpty" operator?
It emits the default value if the source completes without having emitted any value.
It could be helpful in several scenarios.
import { of } from 'rxjs';
import { map, defaultIfEmpty } from 'rxjs/operators';
// source2 doesn't have any values; using defaultIfEmpty, we can have a "default" value.
const source1 = of().pipe(
defaultIfEmpty('Hello There')
);
source1.subscribe(x => console.log(x));
// source1 has a value
const source2 = of('Hello World').pipe(
defaultIfEmpty('Hello There')
);
source2.subscribe(x => console.log(x));
Live Code
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