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