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import { Observable } from '../Observable';
import { SchedulerLike } from '../types';
/**
* A simple Observable that emits no items to the Observer and immediately
* emits a complete notification.
*
* <span class="informal">Just emits 'complete', and nothing else.</span>
*
* 
*
* A simple Observable that only emits the complete notification. It can be used
* for composing with other Observables, such as in a {@link mergeMap}.
*
* ## Examples
*
* Log complete notification
*
* ```ts
* import { EMPTY } from 'rxjs';
*
* EMPTY.subscribe({
* next: () => console.log('Next'),
* complete: () => console.log('Complete!')
* });
*
* // Outputs
* // Complete!
* ```
*
* Emit the number 7, then complete
*
* ```ts
* import { EMPTY, startWith } from 'rxjs';
*
* const result = EMPTY.pipe(startWith(7));
* result.subscribe(x => console.log(x));
*
* // Outputs
* // 7
* ```
*
* Map and flatten only odd numbers to the sequence `'a'`, `'b'`, `'c'`
*
* ```ts
* import { interval, mergeMap, of, EMPTY } from 'rxjs';
*
* const interval$ = interval(1000);
* const result = interval$.pipe(
* mergeMap(x => x % 2 === 1 ? of('a', 'b', 'c') : EMPTY),
* );
* result.subscribe(x => console.log(x));
*
* // Results in the following to the console:
* // x is equal to the count on the interval, e.g. (0, 1, 2, 3, ...)
* // x will occur every 1000ms
* // if x % 2 is equal to 1, print a, b, c (each on its own)
* // if x % 2 is not equal to 1, nothing will be output
* ```
*
* @see {@link Observable}
* @see {@link NEVER}
* @see {@link of}
* @see {@link throwError}
*/
export const EMPTY = new Observable<never>((subscriber) => subscriber.complete());
/**
* @param scheduler A {@link SchedulerLike} to use for scheduling
* the emission of the complete notification.
* @deprecated Replaced with the {@link EMPTY} constant or {@link scheduled} (e.g. `scheduled([], scheduler)`). Will be removed in v8.
*/
export function empty(scheduler?: SchedulerLike) {
return scheduler ? emptyScheduled(scheduler) : EMPTY;
}
function emptyScheduled(scheduler: SchedulerLike) {
return new Observable<never>((subscriber) => scheduler.schedule(() => subscriber.complete()));
}