Creates an Observable that emits no items to the Observer and immediately
emits an error notification.
throwError(error: any, scheduler?: SchedulerLike): Observable<never>
Parameters
| error |
The particular Error to pass to the error notification.
|
| scheduler |
Optional. Default is undefined.
A SchedulerLike to use for scheduling
the emission of the error notification.
|
Returns
Observable<never>: An error Observable: emits only the error notification
using the given error argument.
Description
Just emits 'error', and nothing else.
This static operator is useful for creating a simple Observable that only
emits the error notification. It can be used for composing with other
Observables, such as in a mergeMap.
Examples
Emit the number 7, then emit an error
import { throwError, concat, of } from 'rxjs';
const result = concat(of(7), throwError(new Error('oops!')));
result.subscribe(x => console.log(x), e => console.error(e));
// Logs:
// 7
// Error: oops!
Map and flatten numbers to the sequence 'a', 'b', 'c', but throw an error for 2
import { throwError, interval, of } from 'rxjs';
import { mergeMap } from 'rxjs/operators';
interval(1000).pipe(
mergeMap(x => x === 2
? throwError('Twos are bad')
: of('a', 'b', 'c')
),
).subscribe(x => console.log(x), e => console.error(e));
// Logs:
// a
// b
// c
// a
// b
// c
// Twos are bad