Getting DIV id based on x & y position

Question

The problem I\'m trying to solve is \"What\'s at this position?\"

It\'s fairly trivial to get the x/y position (offset) of a DIV, but what about the reverse? How do

Answer 1

You might find it's more efficient to traverse the DOM tree once when the page is loaded, get all elements' positions and sizes, and store them in an array/hash/etc. If you design the data structure well, you should be able to find an element at the given coordinates fairly quickly when you need it later.

Consider how often you will need to detect an element, and compare that to how often the elements on the page will change. You would be balancing the number of times you have to re-compute all the element locations (an expensive computation) against the number of times you'd actually use the computed information (relatively cheap, I hope).