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import { Observable } from '../Observable'; import { pairwise as higherOrder } from '../operators/pairwise'; /** * Groups pairs of consecutive emissions together and emits them as an array of * two values. * * <span class="informal">Puts the current value and previous value together as * an array, and emits that.</span> * * <img src="./img/pairwise.png" width="100%"> * * The Nth emission from the source Observable will cause the output Observable * to emit an array [(N-1)th, Nth] of the previous and the current value, as a * pair. For this reason, `pairwise` emits on the second and subsequent * emissions from the source Observable, but not on the first emission, because * there is no previous value in that case. * * @example <caption>On every click (starting from the second), emit the relative distance to the previous click</caption> * var clicks = Rx.Observable.fromEvent(document, 'click'); * var pairs = clicks.pairwise(); * var distance = pairs.map(pair => { * var x0 = pair[0].clientX; * var y0 = pair[0].clientY; * var x1 = pair[1].clientX; * var y1 = pair[1].clientY; * return Math.sqrt(Math.pow(x0 - x1, 2) + Math.pow(y0 - y1, 2)); * }); * distance.subscribe(x => console.log(x)); * * @see {@link buffer} * @see {@link bufferCount} * * @return {Observable<Array<T>>} An Observable of pairs (as arrays) of * consecutive values from the source Observable. * @method pairwise * @owner Observable */ export function pairwise<T>(this: Observable<T>): Observable<[T, T]> { return higherOrder()(this) as Observable<[T, T]>; }
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49 entries across 49 versions & 4 rubygems