JSFiddle - React, Tailwind, and code Playground

HTML

<div id=a>
    <div id=inner_a></div>
</div>
<div id=b>
    <div id=inner_b></div>
</div>
<div id=c>
    <div id=inner_c></div>
</div>
<p></p>

CSS

div {
    width: 100px;
    height: 100px;
    background: blue;
    margin: 10px;
}
div > div {
    width: 50px;
    height: 50px;
    background: green;
}

JavaScript

var pos = {x: 0, y: 0};
$(document).on("keyup click", function() { $("p").text(document.elementFromPoint(pos.x, pos.y).id); });
$(document).mousemove(function(event) { pos.x = event.clientX; pos.y = event.clientY; });