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rxjs

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Reactive Extensions for modern JavaScript

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import { OperatorFunction } from '../types'; /** * 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> * * ![](pairwise.png) * * 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 * * On every click (starting from the second), emit the relative distance to the previous click * * ```ts * import { fromEvent, pairwise, map } from 'rxjs'; * * const clicks = fromEvent<PointerEvent>(document, 'click'); * const pairs = clicks.pipe(pairwise()); * const distance = pairs.pipe( * map(([first, second]) => { * const x0 = first.clientX; * const y0 = first.clientY; * const x1 = second.clientX; * const y1 = second.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 A function that returns an Observable of pairs (as arrays) of * consecutive values from the source Observable. */ export declare function pairwise<T>(): OperatorFunction<T, [T, T]>; //# sourceMappingURL=pairwise.d.ts.map