https://bcnsostenible.cat/gl_web/js/plugins/jquery.scrollToTop.js

1/*!
2    jQuery scrollTopTop v1.0 - 2013-03-15
3    (c) 2013 Yang Zhao - geniuscarrier.com
4    license: http://www.opensource.org/licenses/mit-license.php
5*/
6(function($) {
7    $.fn.scrollToTop = function(options) {
8        var config = {
9            "speed" : 800,
10            "offsetTop" : 100
11        };
12
13        if (options) {
14            $.extend(config,options);
15        }
16
17        return this.each(function() {
18
19            var $this = $(this);
20
21            $(window).scroll(function() {
22                if ($(this).scrollTop() > config.offsetTop) {
23                    $this.fadeIn();
24                } else {
25                    $this.fadeOut();
26                }
27            });
28
29            $this.click(function(e) {
30                e.preventDefault();
31                $("body, html").animate({
32                    scrollTop : 0
33                }, config.speed);
34            });
35
36        });
37    };
38})(jQuery);