How to track the appearance of a div block?

Question

JavaScript

Hello!
How can you track a div block?
There are, let's say, 4 div blocks with the "post" class.
When the mouse scrolls, the block appears and how are objects tracked in jquery at all?

Answer 1

Block appearance in viewport or appearance in DOM?
In the first case, track the scroll and compare the scroll amount with the block coordinates.
In the second - MutationObserver