[英]Get difference between last two values of an RxJS Observable
I have an observable tracking the scroll position我有一个可观察的跟踪滚动位置
const scroll = Observable
.fromEvent(document, 'scroll')
.map(e => window.pageYOffset)
.startWith(0)
I would like to have a second observable tracking the scroll delta (newScroll - lastScroll)
我想要第二个 observable 跟踪滚动增量
(newScroll - lastScroll)
const scrollDelta = scroll
// ???
.subscribe(delta => console.log('delta:', delta) )
How to implement something like this?如何实现这样的事情? I've tried with scan with no success.
我试过扫描但没有成功。 Thx
谢谢
老问题,但要加信息的RxJS 5版本,其中API面已经有所改变,我花了一些时间来找到答案:相当于pairwise
会bufferWithCount(2,1)
(V4)或bufferCount(2,1)
(v5)。
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