I\'ve seen a few questions like this in my search, but either the question didn\'t get answered properly or no answer was given. So, I\'ll ask again.
It solved here! They use css and JS.
.child:hover .child-menu { display: block; }
.parent { overflow-y:auto; overflow-x:hidden; width:100px; height:150px }
.child { position:static; }
.child-menu { position:absolute; display:inline-block; display: none; }
https://css-tricks.com/popping-hidden-overflow/
https://jsfiddle.net/68fBE/2/