javascript 获取 RxJS Observable 的最后两个值之间的差异
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Get difference between last two values of an RxJS Observable
提问by Efflam Daniel
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? I've tried with scan with no success. Thx
如何实现这样的事情？我试过扫描但没有成功。谢谢
回答by brokenalarms
Old question, but to add info for RxJS version 5, where the API surface has changed somewhat and it took me some time to find the answer: the equivalent to pairwisewould be bufferWithCount(2,1)(v4) or bufferCount(2,1)(v5).
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是bufferWithCount(2,1)（V4）或bufferCount(2,1)（V5）。
