https://www.a-depeche.jp/blog/wp-content/themes/xeory_base/lib/js/jquery.pagetop.js?ver=6.2.13

1;(function ( $, window, document, undefined ) {
2
3$(function(){
4  $(window).scroll( function(){
5    if( $(this).scrollTop() > 150 ){
6      $('.pagetop').addClass('show');
7    } else {
8      $('.pagetop').removeClass('show');
9    }
10  });
11  $('.pagetop').click(function(){
12    var speed = 500;
13    var href= $(this).attr("href");
14    var target = $(href == "#" || href == "" ? 'html' : href);
15    var position = target.offset().top;
16    $("html, body").animate({scrollTop:position}, speed, "swing");
17    return false;
18  });
19});
20
21})(jQuery, window, document);