Начинающий-Js-кодер,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
div.act{
background-color: #FFD700;
}
div.act div{
background-color: #FFFFFF;
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
$("div").on("mouseover mouseout", function(event) {
event.stopPropagation();
$(this).toggleClass("act")
})
});
</script>
</head>
<body>
<div style="border: 2px black solid; padding:50px; height: 100px;" id="nested1">
<div style="border: 1px blue solid; height: 100px; text-align:center;line-height:100px" id="nested2">
DROP
</div>
</div>
</body>
</html>