JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div id="weblinks">
</div>

<a href="#" id="scrollup">Scroll up</a>

CSS

html {
    height: 5000px
}

#weblinks {
    background: #4679BD;
}

div {
    height: 300px;  
    width: 100%;
    border: 1px solid #ccc;
    margin-bottom: 20px;
    background: #ddd
}

#scrollup {
    width: 100px;
    height: 30px;
    color: #fff;
    background: #ff0000;
    position: fixed;
    top: 20px;
    left: 20px;
    display: none;
}

JavaScript

$(document).ready(function () {

var elem   = $('#weblinks');  
    
var bottom = $(elem).position().top+$(elem).outerHeight(true)

    $(window).scroll(function () {
        if ($(this).scrollTop() > bottom) {
            $('#scrollup').fadeIn();
        } else {
            $('#scrollup').fadeOut();
        }
    });

    $('#scrollup').click(function () {
        $("html, body").animate({ scrollTop: 0 }, 500);
        return false;
    });

});