scroll to both direction

[vinnitu]

Hi!

I want to scroll remote records with timestamp field.
Record can has different height because can has different type and content length
I don't want to save all items after fetch new portion data. I prefer to trunk array.
Can you show me how to can we scroll up and scroll down?

[adress in browser: `http://exaple.site?from=${topvisibletlement.time}`

<markerWhenFetchUp>
unvisibleItem
unvisibleItem
-----top screen----
topVisibleItem
visibleItem
... different number of visible elements 
visibleItem
-----bottom screen---
unvsibleItem
unvisibleItem
<markerWhenFetchDown>

How to change address in browser when do scroll?
How to start when we have only address with query from=start time?
I think we can fetch batch fixed number records from server up and down from start time.
But how to stay at visible element at top of screen after records was fetched and pushed?