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node_modules/rxjs/_esm2015/operators/count.js

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+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 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 (source) => source.lift(new CountOperator(predicate, source));
+}
+class CountOperator {
+    constructor(predicate, source) {
+        this.predicate = predicate;
+        this.source = source;
+    }
+    call(subscriber, source) {
+        return source.subscribe(new CountSubscriber(subscriber, this.predicate, this.source));
+    }
+}
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+class CountSubscriber extends Subscriber {
+    constructor(destination, predicate, source) {
+        super(destination);
+        this.predicate = predicate;
+        this.source = source;
+        this.count = 0;
+        this.index = 0;
+    }
+    _next(value) {
+        if (this.predicate) {
+            this._tryPredicate(value);
+        }
+        else {
+            this.count++;
+        }
+    }
+    _tryPredicate(value) {
+        let result;
+        try {
+            result = this.predicate(value, this.index++, this.source);
+        }
+        catch (err) {
+            this.destination.error(err);
+            return;
+        }
+        if (result) {
+            this.count++;
+        }
+    }
+    _complete() {
+        this.destination.next(this.count);
+        this.destination.complete();
+    }
+}
+//# sourceMappingURL=count.js.map