How to detect elements overlapping (overlaying) using JavaScript?

Question

How to detect overlap HTML elements, using JavaScript?

I have an item list (

). It slides up and down using JavaScript. When it slides down, de

Answer 1

function isObjOnObj(a,b){
    var al = a.left;
    var ar = a.left+a.width;
    var bl = b.left;
    var br = b.left+b.width;

    var at = a.top;
    var ab = a.top+a.height;
    var bt = b.top;
    var bb = b.top+b.height;

    if(bl>ar || brab || bbal && blal && brat && btat && bb