53 lines
2.2 KiB
JavaScript
53 lines
2.2 KiB
JavaScript
import { count as higherOrder } from '../operators/count';
|
|
/**
|
|
* Counts the number of emissions on the source and emits that number when the
|
|
* source completes.
|
|
*
|
|
* <span class="informal">Tells how many values were emitted, when the source
|
|
* completes.</span>
|
|
*
|
|
* <img src="./img/count.png" width="100%">
|
|
*
|
|
* `count` transforms an Observable that emits values into an Observable that
|
|
* emits a single value that represents the number of values emitted by the
|
|
* source Observable. If the source Observable terminates with an error, `count`
|
|
* will pass this error notification along without emitting a value first. If
|
|
* the source Observable does not terminate at all, `count` will neither emit
|
|
* a value nor terminate. This operator takes an optional `predicate` function
|
|
* as argument, in which case the output emission will represent the number of
|
|
* source values that matched `true` with the `predicate`.
|
|
*
|
|
* @example <caption>Counts how many seconds have passed before the first click happened</caption>
|
|
* var seconds = Rx.Observable.interval(1000);
|
|
* var clicks = Rx.Observable.fromEvent(document, 'click');
|
|
* var secondsBeforeClick = seconds.takeUntil(clicks);
|
|
* var result = secondsBeforeClick.count();
|
|
* result.subscribe(x => console.log(x));
|
|
*
|
|
* @example <caption>Counts how many odd numbers are there between 1 and 7</caption>
|
|
* var numbers = Rx.Observable.range(1, 7);
|
|
* var result = numbers.count(i => i % 2 === 1);
|
|
* result.subscribe(x => console.log(x));
|
|
*
|
|
* // Results in:
|
|
* // 4
|
|
*
|
|
* @see {@link max}
|
|
* @see {@link min}
|
|
* @see {@link reduce}
|
|
*
|
|
* @param {function(value: T, i: number, source: Observable<T>): boolean} [predicate] A
|
|
* boolean function to select what values are to be counted. It is provided with
|
|
* arguments of:
|
|
* - `value`: the value from the source Observable.
|
|
* - `index`: the (zero-based) "index" of the value from the source Observable.
|
|
* - `source`: the source Observable instance itself.
|
|
* @return {Observable} An Observable of one number that represents the count as
|
|
* described above.
|
|
* @method count
|
|
* @owner Observable
|
|
*/
|
|
export function count(predicate) {
|
|
return higherOrder(predicate)(this);
|
|
}
|
|
//# sourceMappingURL=count.js.map
|