JSFiddle - React, Tailwind, and code Playground

HTML

<div class="stage">
  <div class="bar"></div>
</div>

CSS

.stage{
  height:400px;
  width:auto;
  background:#ccc;
  }
.bar{
  height:20px;
  width:auto;
  background:#000;
  display:none;
  }

JavaScript

var countdown;
$(".stage").hover(function() {
  $(".bar").fadeIn();
    fadeOutBar();
}, function(e){
    $(".bar").fadeOut();
});
$('.stage').mousemove(function() {
    $(".bar").fadeIn();
    fadeOutBar();
});
function fadeOutBar() {
    countdown = setTimeout(function() {
      $(".bar").fadeOut();
    }, 2000);
}