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Contents
"use strict";
var scan_1 = require('../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
*/
function scan(accumulator, seed) {
if (arguments.length >= 2) {
return scan_1.scan(accumulator, seed)(this);
}
return scan_1.scan(accumulator)(this);
}
exports.scan = scan;
//# sourceMappingURL=scan.js.map
Version data entries
49 entries across 49 versions & 4 rubygems