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37 lines
1.4 KiB
37 lines
1.4 KiB
import { OperatorFunction } from '../interfaces'; |
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/** |
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* Groups pairs of consecutive emissions together and emits them as an array of |
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* two values. |
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* |
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* <span class="informal">Puts the current value and previous value together as |
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* an array, and emits that.</span> |
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* |
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* <img src="./img/pairwise.png" width="100%"> |
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* |
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* The Nth emission from the source Observable will cause the output Observable |
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* to emit an array [(N-1)th, Nth] of the previous and the current value, as a |
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* pair. For this reason, `pairwise` emits on the second and subsequent |
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* emissions from the source Observable, but not on the first emission, because |
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* there is no previous value in that case. |
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* |
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* @example <caption>On every click (starting from the second), emit the relative distance to the previous click</caption> |
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* var clicks = Rx.Observable.fromEvent(document, 'click'); |
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* var pairs = clicks.pairwise(); |
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* var distance = pairs.map(pair => { |
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* var x0 = pair[0].clientX; |
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* var y0 = pair[0].clientY; |
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* var x1 = pair[1].clientX; |
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* var y1 = pair[1].clientY; |
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* return Math.sqrt(Math.pow(x0 - x1, 2) + Math.pow(y0 - y1, 2)); |
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* }); |
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* distance.subscribe(x => console.log(x)); |
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* |
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* @see {@link buffer} |
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* @see {@link bufferCount} |
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* |
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* @return {Observable<Array<T>>} An Observable of pairs (as arrays) of |
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* consecutive values from the source Observable. |
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* @method pairwise |
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* @owner Observable |
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*/ |
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export declare function pairwise<T>(): OperatorFunction<T, [T, T]>;
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