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import { MonoTypeOperatorFunction, SchedulerLike } from '../types';
/**
* Emits the most recently emitted value from the source Observable within
* periodic time intervals.
*
* <span class="informal">Samples the source Observable at periodic time
* intervals, emitting what it samples.</span>
*
* ![](sampleTime.png)
*
* `sampleTime` periodically looks at the source Observable and emits whichever
* value it has most recently emitted since the previous sampling, unless the
* source has not emitted anything since the previous sampling. The sampling
* happens periodically in time every `period` milliseconds (or the time unit
* defined by the optional `scheduler` argument). The sampling starts as soon as
* the output Observable is subscribed.
*
* ## Example
* Every second, emit the most recent click at most once
* ```ts
* import { fromEvent } from 'rxjs';
* import { sampleTime } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const result = clicks.pipe(sampleTime(1000));
* result.subscribe(x => console.log(x));
* ```
*
* @see {@link auditTime}
* @see {@link debounceTime}
* @see {@link delay}
* @see {@link sample}
* @see {@link throttleTime}
*
* @param {number} period The sampling period expressed in milliseconds or the
* time unit determined internally by the optional `scheduler`.
* @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for
* managing the timers that handle the sampling.
* @return {Observable<T>} An Observable that emits the results of sampling the
* values emitted by the source Observable at the specified time interval.
* @method sampleTime
* @owner Observable
*/
export declare function sampleTime<T>(period: number, scheduler?: SchedulerLike): MonoTypeOperatorFunction<T>;