JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header">HEADER</div>

CSS

body {
    height: 2000px;
    margin: 0;
}

body > #header{position:fixed;}

#header {
    width: 100%;
    position: fixed;
    z-index:9000;
    overflow: auto;
    background: #e6e6e6;
    text-align: center;
    padding: 10px 0;
    transition: all 0.5s linear;
}

#header.active {
     box-shadow: 0 0 10px rgba(0,0,0,0.4);   
}

JavaScript

$(window).scroll(function() {     
    var scroll = $(window).scrollTop();
    if (scroll > 0) {
        $("#header").addClass("active");
    }
    else {
        $("#header").removeClass("active");
    }
});