64 lines
1.7 KiB
Plaintext
64 lines
1.7 KiB
Plaintext
import { OperatorFunction } from '../types';
|
|
/**
|
|
* Emits `false` if the input Observable emits any values, or emits `true` if the
|
|
* input Observable completes without emitting any values.
|
|
*
|
|
* <span class="informal">Tells whether any values are emitted by an Observable.</span>
|
|
*
|
|
* 
|
|
*
|
|
* `isEmpty` transforms an Observable that emits values into an Observable that
|
|
* emits a single boolean value representing whether or not any values were
|
|
* emitted by the source Observable. As soon as the source Observable emits a
|
|
* value, `isEmpty` will emit a `false` and complete. If the source Observable
|
|
* completes having not emitted anything, `isEmpty` will emit a `true` and
|
|
* complete.
|
|
*
|
|
* A similar effect could be achieved with {@link count}, but `isEmpty` can emit
|
|
* a `false` value sooner.
|
|
*
|
|
* ## Examples
|
|
*
|
|
* Emit `false` for a non-empty Observable
|
|
*
|
|
* ```ts
|
|
* import { Subject, isEmpty } from 'rxjs';
|
|
*
|
|
* const source = new Subject<string>();
|
|
* const result = source.pipe(isEmpty());
|
|
*
|
|
* source.subscribe(x => console.log(x));
|
|
* result.subscribe(x => console.log(x));
|
|
*
|
|
* source.next('a');
|
|
* source.next('b');
|
|
* source.next('c');
|
|
* source.complete();
|
|
*
|
|
* // Outputs
|
|
* // 'a'
|
|
* // false
|
|
* // 'b'
|
|
* // 'c'
|
|
* ```
|
|
*
|
|
* Emit `true` for an empty Observable
|
|
*
|
|
* ```ts
|
|
* import { EMPTY, isEmpty } from 'rxjs';
|
|
*
|
|
* const result = EMPTY.pipe(isEmpty());
|
|
* result.subscribe(x => console.log(x));
|
|
*
|
|
* // Outputs
|
|
* // true
|
|
* ```
|
|
*
|
|
* @see {@link count}
|
|
* @see {@link EMPTY}
|
|
*
|
|
* @return A function that returns an Observable that emits boolean value
|
|
* indicating whether the source Observable was empty or not.
|
|
*/
|
|
export declare function isEmpty<T>(): OperatorFunction<T, boolean>;
|
|
//# sourceMappingURL=isEmpty.d.ts.map |