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import { Observable } from '../Observable';
import { OperatorFunction } from '../types';
/**
* Buffers the source Observable values, using a factory function of closing
* Observables to determine when to close, emit, and reset the buffer.
*
* <span class="informal">Collects values from the past as an array. When it
* starts collecting values, it calls a function that returns an Observable that
* tells when to close the buffer and restart collecting.</span>
*
* ![](bufferWhen.png)
*
* Opens a buffer immediately, then closes the buffer when the observable
* returned by calling `closingSelector` function emits a value. When it closes
* the buffer, it immediately opens a new buffer and repeats the process.
*
* ## Example
*
* Emit an array of the last clicks every [1-5] random seconds
*
* ```ts
* import { fromEvent, interval } from 'rxjs';
* import { bufferWhen } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const buffered = clicks.pipe(bufferWhen(() =>
* interval(1000 + Math.random() * 4000)
* ));
* buffered.subscribe(x => console.log(x));
* ```
*
*
* @see {@link buffer}
* @see {@link bufferCount}
* @see {@link bufferTime}
* @see {@link bufferToggle}
* @see {@link windowWhen}
*
* @param {function(): Observable} closingSelector A function that takes no
* arguments and returns an Observable that signals buffer closure.
* @return {Observable<T[]>} An observable of arrays of buffered values.
* @method bufferWhen
* @owner Observable
*/
export declare function bufferWhen<T>(closingSelector: () => Observable<any>): OperatorFunction<T, T[]>;