Scenario
When our Observable<E> errors out, we want to emit the string fallback value OOOPS .
Approach
oops.pipe(catchError(err => of('OOOPS')))Demo
The first part of the demo uses throwError to error out the catchMeIfYouCan:Observable<string> , and therefore only the error handler is called, and neither the next nor the complete handlers are called.
let catchMeIfYouCan: Observable<string> = throwError("Catch me if you can");catchMeIfYouCan.subscribe(() => console.log("Next handler will not execute"),e => console.log(e),() => console.log("Completion handler will not execute"));
In the second part we pipe through catchError and emit the fallback, and now both the next and complete handlers are called and the error handler is not called.
