JSFiddle - React, Tailwind, and code Playground

by webxz

HTML

<body>
<div class="menu">меню</div>
</body>

CSS

body {
  height: 20000px;
}
.menu {
  background-color: red;
  position: fixed;
  top:0;left:0;right:0;
  padding: 10px;
}
.new-class {
  opacity: .6
}

JavaScript

var removeTimeoutID, $menu = $('.menu');    
$(window).scroll(function() {    
    clearTimeout(removeTimeoutID);
    $menu.addClass('new-class');
    removeTimeoutID = setTimeout(function(){
        $menu.removeClass('new-class');
    }, 400);
});