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48 lines
1.8 KiB
48 lines
1.8 KiB
"use strict"; |
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var scan_1 = require('../operators/scan'); |
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/* tslint:enable:max-line-length */ |
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/** |
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* Applies an accumulator function over the source Observable, and returns each |
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* intermediate result, with an optional seed value. |
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* |
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* <span class="informal">It's like {@link reduce}, but emits the current |
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* accumulation whenever the source emits a value.</span> |
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* |
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* <img src="./img/scan.png" width="100%"> |
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* |
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* Combines together all values emitted on the source, using an accumulator |
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* function that knows how to join a new source value into the accumulation from |
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* the past. Is similar to {@link reduce}, but emits the intermediate |
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* accumulations. |
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* |
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* Returns an Observable that applies a specified `accumulator` function to each |
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* item emitted by the source Observable. If a `seed` value is specified, then |
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* that value will be used as the initial value for the accumulator. If no seed |
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* value is specified, the first item of the source is used as the seed. |
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* |
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* @example <caption>Count the number of click events</caption> |
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* var clicks = Rx.Observable.fromEvent(document, 'click'); |
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* var ones = clicks.mapTo(1); |
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* var seed = 0; |
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* var count = ones.scan((acc, one) => acc + one, seed); |
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* count.subscribe(x => console.log(x)); |
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* |
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* @see {@link expand} |
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* @see {@link mergeScan} |
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* @see {@link reduce} |
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* |
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* @param {function(acc: R, value: T, index: number): R} accumulator |
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* The accumulator function called on each source value. |
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* @param {T|R} [seed] The initial accumulation value. |
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* @return {Observable<R>} An observable of the accumulated values. |
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* @method scan |
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* @owner Observable |
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*/ |
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function scan(accumulator, seed) { |
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if (arguments.length >= 2) { |
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return scan_1.scan(accumulator, seed)(this); |
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} |
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return scan_1.scan(accumulator)(this); |
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} |
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exports.scan = scan; |
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//# sourceMappingURL=scan.js.map
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