JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main">
</div>
<footer class="nav-down">
123
</footer>

CSS

* { 
margin:0;
padding:0;
color: transparent;
}
.main {
width:100%;
height:1500px;
}
.nav-down {
    bottom: -40px;
}
footer {
    -webkit-backface-visibility: hidden;
    background: #000;
    height: 40px;
    position: fixed;
    bottom: 0;
    transition: bottom 0.2s ease-in-out;
    width: 100%;
    z-index: 1000;
    border-top:1px solid #000;
}

JavaScript

// Hide Footer on on scroll down
var didScroll;
var lastScrollTop = 0;
var delta = 5;
var navbarHeight = $('footer').outerHeight();

$(window).scroll(function(event){
    didScroll = true;
});

setInterval(function() {
    if (didScroll) {
        hasScrolled();
        didScroll = false;
    }
}, 250);

function hasScrolled() {
    var st = $(this).scrollTop();
    
    // Make sure they scroll more than delta
    if(Math.abs(lastScrollTop - st) <= delta)
        return;
    
    if (st > lastScrollTop && st > navbarHeight){

        $('footer').removeClass('nav-up').addClass('nav-down');
    } else {

        if(st + $(window).height() < $(document).height()) {
            $('footer').removeClass('nav-down').addClass('nav-up');
        }
    }
    
    lastScrollTop = st;
};