Detect specific element when scrolled over a set point in another element

I've seen solutions such as this: Detect when a position: fixed; element crosses over another element

I've even implemented a similar concept that is working, for the most part.

That said, I'm curious to know if there is a better method I'm unaware of that basically allows us to capture an element - any element - that scrolls past another specific element's location. In my case, it would be the top of a fixed container observing anything that enters that point.

Are other solutions out there, or is my current reference I linked to above really the only feasible way to handle this behavior? I've searched like crazy for the past few days, but it's a tough topic to find a lot of solid answers on.