JSFiddle - React, Tailwind, and code Playground

HTML

<div class="preloader">
        <div class="preloder-wrap">
            <div class="preloder-inner"> 
                <div class="ball"></div> 
                <div class="ball"></div> 
                <div class="ball"></div> 
                <div class="ball"></div> 
                <div class="ball"></div> 
                <div class="ball"></div> 
                <div class="ball"></div>
            </div>
        </div>
    </div><!--/.preloader-->
    <header id="navigation"> 
        <div class="navbar navbar-inverse navbar-fixed-top" role="banner"> 
            <div class="container"> 
                <div class="navbar-header"> 
            </div>
        </div>
            </div>
        </header>


----------  中略 ----------  


<a href="#home" class="page-top"><i class="fa fa-chevron-up" aria-hidden="true"></i><br>PAGE TOP</a>

CSS

.page-top {
    position: fixed;
    bottom: 20px;
    right: 20px;
    font-size: 77%;
}
.page-top a {
    background: #666;
    text-decoration: none;
    color: #fff;
    width: 100px;
    padding: 30px 0;
    text-align: center;
    display: block;
    border-radius: 5px;
}
.page-top a:hover {
    text-decoration: none;
    background: #999;
}


#navigation {
  padding-bottom: 320vh;/* for test */
}

JavaScript

$(function() {
    var pageTop = $('.page-top');
    pageTop.hide();
    $(window).scroll(function () {
        if ($(this).scrollTop() > 600) {
            pageTop.fadeIn();
        } else {
            pageTop.fadeOut();
        }
    });
    pageTop.click(function () {
        $('body, html').animate({scrollTop:0}, 500, 'swing');
        return false;
    });
    $(".preloader").delay(1600).fadeOut("slow").remove();

    // Slider Height
    var slideHeight = $(window).height();
    $('#home .carousel-inner .item, #home .video-container').css('height',slideHeight);

    $(window).resize(function(){'use strict',
        $('#home .carousel-inner .item, #home .video-container').css('height',slideHeight);
    });
});

// User define function
function Scroll() {
    var contentTop      =   [];
    var contentBottom   =   [];
    var winTop      =   $(window).scrollTop();
    var rangeTop    =   200;
    var rangeBottom =   500;
    $('.navbar-collapse').find('.scroll a').each(function(){
        contentTop.push( $( $(this).attr('href') ).offset().top);
        contentBottom.push( $( $(this).attr('href') ).offset().top + $( $(this).attr('href') ).height() );
    })
    $.each( contentTop, function(i){
        if ( winTop > contentTop[i] - rangeTop ){
            $('.navbar-collapse li.scroll')
            .removeClass('active')
            .eq(i).addClass('active');
        }
    });
};