45 lines
1.7 KiB
TypeScript
45 lines
1.7 KiB
TypeScript
|
import { MonoTypeOperatorFunction } from '../types';
|
||
|
|
/**
|
||
|
|
* Emits only the last `count` values emitted by the source Observable.
|
||
|
|
*
|
||
|
|
* <span class="informal">Remembers the latest `count` values, then emits those
|
||
|
|
* only when the source completes.</span>
|
||
|
|
*
|
||
|
|
* 
|
||
|
|
*
|
||
|
|
* `takeLast` returns an Observable that emits at most the last `count` values
|
||
|
|
* emitted by the source Observable. If the source emits fewer than `count`
|
||
|
|
* values then all of its values are emitted. This operator must wait until the
|
||
|
|
* `complete` notification emission from the source in order to emit the `next`
|
||
|
|
* values on the output Observable, because otherwise it is impossible to know
|
||
|
|
* whether or not more values will be emitted on the source. For this reason,
|
||
|
|
* all values are emitted synchronously, followed by the complete notification.
|
||
|
|
*
|
||
|
|
* ## Example
|
||
|
|
* Take the last 3 values of an Observable with many values
|
||
|
|
* ```ts
|
||
|
|
* import { range } from 'rxjs';
|
||
|
|
* import { takeLast } from 'rxjs/operators';
|
||
|
|
*
|
||
|
|
* const many = range(1, 100);
|
||
|
|
* const lastThree = many.pipe(takeLast(3));
|
||
|
|
* lastThree.subscribe(x => console.log(x));
|
||
|
|
* ```
|
||
|
|
*
|
||
|
|
* @see {@link take}
|
||
|
|
* @see {@link takeUntil}
|
||
|
|
* @see {@link takeWhile}
|
||
|
|
* @see {@link skip}
|
||
|
|
*
|
||
|
|
* @throws {ArgumentOutOfRangeError} When using `takeLast(i)`, it delivers an
|
||
|
|
* ArgumentOutOrRangeError to the Observer's `error` callback if `i < 0`.
|
||
|
|
*
|
||
|
|
* @param {number} count The maximum number of values to emit from the end of
|
||
|
|
* the sequence of values emitted by the source Observable.
|
||
|
|
* @return {Observable<T>} An Observable that emits at most the last count
|
||
|
|
* values emitted by the source Observable.
|
||
|
|
* @method takeLast
|
||
|
|
* @owner Observable
|
||
|
|
*/
|
||
|
|
export declare function takeLast<T>(count: number): MonoTypeOperatorFunction<T>;
|