79 lines
2.7 KiB
JavaScript
79 lines
2.7 KiB
JavaScript
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/** PURE_IMPORTS_START .._Subscriber PURE_IMPORTS_END */
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var __extends = (this && this.__extends) || function (d, b) {
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for (var p in b)
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if (b.hasOwnProperty(p))
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d[p] = b[p];
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function __() { this.constructor = d; }
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d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
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};
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import { Subscriber } from '../Subscriber';
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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 function pairwise() {
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return function (source) { return source.lift(new PairwiseOperator()); };
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}
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var PairwiseOperator = /*@__PURE__*/ (/*@__PURE__*/ function () {
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function PairwiseOperator() {
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}
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PairwiseOperator.prototype.call = function (subscriber, source) {
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return source.subscribe(new PairwiseSubscriber(subscriber));
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};
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return PairwiseOperator;
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}());
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @ignore
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* @extends {Ignored}
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*/
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var PairwiseSubscriber = /*@__PURE__*/ (/*@__PURE__*/ function (_super) {
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__extends(PairwiseSubscriber, _super);
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function PairwiseSubscriber(destination) {
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_super.call(this, destination);
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this.hasPrev = false;
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}
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PairwiseSubscriber.prototype._next = function (value) {
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if (this.hasPrev) {
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this.destination.next([this.prev, value]);
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}
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else {
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this.hasPrev = true;
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}
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this.prev = value;
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};
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return PairwiseSubscriber;
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}(Subscriber));
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//# sourceMappingURL=pairwise.js.map
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