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node_modules/rxjs/_esm5/operator/scan.js

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+/** PURE_IMPORTS_START .._operators_scan PURE_IMPORTS_END */
+import { scan as higherOrderScan } from '../operators/scan';
+/* tslint:enable:max-line-length */
+/**
+ * Applies an accumulator function over the source Observable, and returns each
+ * intermediate result, with an optional seed value.
+ *
+ * <span class="informal">It's like {@link reduce}, but emits the current
+ * accumulation whenever the source emits a value.</span>
+ *
+ * <img src="./img/scan.png" width="100%">
+ *
+ * Combines together all values emitted on the source, using an accumulator
+ * function that knows how to join a new source value into the accumulation from
+ * the past. Is similar to {@link reduce}, but emits the intermediate
+ * accumulations.
+ *
+ * Returns an Observable that applies a specified `accumulator` function to each
+ * item emitted by the source Observable. If a `seed` value is specified, then
+ * that value will be used as the initial value for the accumulator. If no seed
+ * value is specified, the first item of the source is used as the seed.
+ *
+ * @example <caption>Count the number of click events</caption>
+ * var clicks = Rx.Observable.fromEvent(document, 'click');
+ * var ones = clicks.mapTo(1);
+ * var seed = 0;
+ * var count = ones.scan((acc, one) => acc + one, seed);
+ * count.subscribe(x => console.log(x));
+ *
+ * @see {@link expand}
+ * @see {@link mergeScan}
+ * @see {@link reduce}
+ *
+ * @param {function(acc: R, value: T, index: number): R} accumulator
+ * The accumulator function called on each source value.
+ * @param {T|R} [seed] The initial accumulation value.
+ * @return {Observable<R>} An observable of the accumulated values.
+ * @method scan
+ * @owner Observable
+ */
+export function scan(accumulator, seed) {
+    if (arguments.length >= 2) {
+        return higherOrderScan(accumulator, seed)(this);
+    }
+    return higherOrderScan(accumulator)(this);
+}
+//# sourceMappingURL=scan.js.map