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<div class="content" data-ice="content"><h1 data-ice="title">es6/operator/pairwise.js</h1>
<pre class="source-code line-number raw-source-code"><code class="prettyprint linenums" data-ice="content">import { Subscriber } from '../Subscriber';
/**
* 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() {
return this.lift(new PairwiseOperator());
}
var PairwiseOperator = (function () {
function PairwiseOperator() {
}
PairwiseOperator.prototype.call = function (subscriber, source) {
return source._subscribe(new PairwiseSubscriber(subscriber));
};
return PairwiseOperator;
}());
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
var PairwiseSubscriber = (function (_super) {
__extends(PairwiseSubscriber, _super);
function PairwiseSubscriber(destination) {
_super.call(this, destination);
this.hasPrev = false;
}
PairwiseSubscriber.prototype._next = function (value) {
if (this.hasPrev) {
this.destination.next([this.prev, value]);
}
else {
this.hasPrev = true;
}
this.prev = value;
};
return PairwiseSubscriber;
}(Subscriber));
//# sourceMappingURL=pairwise.js.map</code></pre>
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