React useScroll Hook keep track of previousScrollTop - reactjs

Question

So I've followed this:
https://www.pinkdroids.com/blog/moving-header-react-hooks-context/
And managed to get it working on one app.
I'm not replicating what I did in another app and it's not working.
I've got as far as working out that my previousScrollTop and currentScrollTop are always the same – therefore no direction is being added
But why are they the same!!!
I've gone as far as copy and pasting the code so no issues there.
Could this be a problem with memo?
with my lodash import?
Not getting any errors.
UPDATE*
The problem is either with useMemo, or useRef in my useScroll hook.
const getScrollPosition = () => {
if (typeof window === 'undefined') {
return 0
}
return (
window.pageYOffset ||
document.documentElement.scrollTop ||
document.body.scrollTop ||
0
)
}
export const useScroll = (timeout = 250) => {
const defaultScrollTop = useMemo(() => getScrollPosition(), [])
const previousScrollTop = useRef(defaultScrollTop)
const [currentScrollTop, setCurrentScrollTop] = useState(defaultScrollTop)
console.log(currentScrollTop)
useEffect(() => {
const handleDocumentScroll = () => {
const scrollTop = getScrollPosition()
setCurrentScrollTop(scrollTop)
console.log(currentScrollTop)
previousScrollTop.current = scrollTop
console.log(previousScrollTop.current)
}
const handleDocumentScrollThrottled = throttle(handleDocumentScroll, timeout)
document.addEventListener('scroll', handleDocumentScrollThrottled)
return () => {
document.removeEventListener('scroll', handleDocumentScrollThrottled)
}
}, [timeout])
return {
scrollTop: currentScrollTop,
previousScrollTop: previousScrollTop.current,
time: timeout,
}
}
UPDATE*
I've managed to work a fix with a setTimeout inside my handleDocumentScroll... Should delay between the values...
But still unsure why this worked before as it was and not now....
const handleDocumentScroll = () => {
const scrollTop = getScrollPosition()
setCurrentScrollTop(scrollTop)
setTimeout(function () {
previousScrollTop.current = scrollTop
}, 200); // update previous 200ms after event fires
}