Scroll events are known to have performance issues. Intersection API is another alternative to keep track of when elements come into view. However scrollTop is still something that would be needed for calculating corresponding rows. It's best to try out this version of implementation as well.

This might help in cases where the scroll event misses the element even for speed that wouldn't come in the category of 'fast'. But overall intersection isn't so much better in catching the element each time than it is in terms of performance, which going by some of the tests done by others, is a huge improvement.