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import { Observable } from '../Observable';
import { SchedulerLike } from '../types';
import { Subscriber } from '../Subscriber';
/**
* Creates an Observable that emits no items to the Observer and immediately
* emits an error notification.
*
* <span class="informal">Just emits 'error', and nothing else.
* </span>
*
* 
*
* 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 {@link mergeMap}.
*
* ## Examples
* ### Emit the number 7, then emit an error
* ```javascript
* 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 13
* ```javascript
* 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
* ```
*
* @see {@link Observable}
* @see {@link empty}
* @see {@link never}
* @see {@link of}
*
* @param {any} error The particular Error to pass to the error notification.
* @param {SchedulerLike} [scheduler] A {@link SchedulerLike} to use for scheduling
* the emission of the error notification.
* @return {Observable} An error Observable: emits only the error notification
* using the given error argument.
* @static true
* @name throwError
* @owner Observable
*/
export function throwError(error: any, scheduler?: SchedulerLike): Observable<never> {
if (!scheduler) {
return new Observable(subscriber => subscriber.error(error));
} else {
return new Observable(subscriber => scheduler.schedule(dispatch, 0, { error, subscriber }));
}
}
interface DispatchArg {
error: any;
subscriber: Subscriber<any>;
}
function dispatch({ error, subscriber }: DispatchArg) {
subscriber.error(error);
}
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