pairwise
RxJS 5 pairwise
HTML
<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/5.0.1/Rx.min.js"></script>
JavaScript
var interval = Rx.Observable.interval(1000);
//Returns: [0,0], [1,0], [1,1], [2,1], [2,2]
interval.pairwise()
.take(15)
.subscribe(console.log);