@reactivex/rxjs

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class="source-code line-number raw-source-code"><code class="prettyprint linenums" data-ice="content">import { Subscriber } from '../Subscriber'; /** * 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 an 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)); * * @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 this.lift(new CountOperator(predicate, this)); } var CountOperator = (function () { function CountOperator(predicate, source) { this.predicate = predicate; this.source = source; } CountOperator.prototype.call = function (subscriber, source) { return source._subscribe(new CountSubscriber(subscriber, this.predicate, this.source)); }; return CountOperator; }()); /** * We need this JSDoc comment for affecting ESDoc. * @ignore * @extends {Ignored} */ var CountSubscriber = (function (_super) { __extends(CountSubscriber, _super); function CountSubscriber(destination, predicate, source) { _super.call(this, destination); this.predicate = predicate; this.source = source; this.count = 0; this.index = 0; } CountSubscriber.prototype._next = function (value) { if (this.predicate) { this._tryPredicate(value); } else { this.count++; } }; CountSubscriber.prototype._tryPredicate = function (value) { var result; try { result = this.predicate(value, this.index++, this.source); } catch (err) { this.destination.error(err); return; } if (result) { this.count++; } }; CountSubscriber.prototype._complete = function () { this.destination.next(this.count); this.destination.complete(); }; return CountSubscriber; }(Subscriber)); //# sourceMappingURL=count.js.map</code></pre> </div> <footer class="footer"> Generated by <a href="https://esdoc.org">ESDoc<span data-ice="esdocVersion">(0.4.8)</span></a> </footer> <script src="script/search_index.js"></script> <script src="script/search.js"></script> <script src="script/pretty-print.js"></script> <script src="script/inherited-summary.js"></script> <script src="script/test-summary.js"></script> <script src="script/inner-link.js"></script> <script src="script/patch-for-local.js"></script> </body> </html>