Smooth Scroll Back to Top Button

scroll-up.js

/* Place this code in your JS file */
jQuery(document).ready(function($){
    // browser window scroll (in pixels) after which the "back to top" link is shown
    var offset = 300,
    //browser window scroll (in pixels) after which the "back to top" link opacity is reduced
        offset_opacity = 1200,
    //duration of the top scrolling animation (in ms)
        scroll_top_duration = 3500,
    //grab the "back to top" link
        $back_to_top = $('.cd-top');

    //hide or show the "back to top" link
    $(window).scroll(function(){
        ( $(this).scrollTop() > offset ) ? $back_to_top.addClass('cd-is-visible') : $back_to_top.removeClass('cd-is-visible cd-fade-out');
        if( $(this).scrollTop() > offset_opacity ) {
            $back_to_top.addClass('cd-fade-out');
        }
    });

    //smooth scroll to top
    $back_to_top.on('click', function(event){
        event.preventDefault();
        $('body,html').animate({
                scrollTop: 10
            }, scroll_top_duration
        );
        $('body,html').animate({
                scrollTop: 0
            }, 0
        );
    });
});

scroll.css

/* Place this code in your CSS file */

.cd-top {
    display: inline-block;
    height: 40px;
    width: 40px;
    position: fixed;
    bottom: 40px;
    right: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.05);
    /* image replacement properties */
    overflow: hidden;
    text-indent: 100%;
    white-space: nowrap;
    background: rgba(232, 98, 86, 0.8) url(../img/cd-top-arrow.svg) no-repeat center 50%;
    visibility: hidden;
    opacity: 0;
    -webkit-transition: opacity .3s 0s, visibility 0s .3s;
    -moz-transition: opacity .3s 0s, visibility 0s .3s;
    transition: opacity .3s 0s, visibility 0s .3s;
}
.cd-top.cd-is-visible, .cd-top.cd-fade-out, .no-touch .cd-top:hover {
    -webkit-transition: opacity .3s 0s, visibility 0s 0s;
    -moz-transition: opacity .3s 0s, visibility 0s 0s;
    transition: opacity .3s 0s, visibility 0s 0s;
}
.cd-top.cd-is-visible {
    /* the button becomes visible */
    visibility: visible;
    opacity: 1;
}
.cd-top.cd-fade-out {
    /* if the user keeps scrolling down, the button is out of focus and becomes less visible */
    opacity: .5;
}
.no-touch .cd-top:hover {
    background-color: #e86256;
    opacity: 1;
}

smooth-scroll-up.html

<!-- Place this code at the bottom of your body but right before you load you scripts in you HTML file -->
<a href="#0" class="cd-top">Top</a>