https://futuresciencenews.com/wp-content/themes/NTTheme/js/BacktoTop.js

1$(document).ready(function() {
2
3$("body").prepend('<a name="PageTop" id="PageTop"></a>');
4$("body").append('<div id="BacktoTop" title="Back to Top"></div>');
5
6scrollButton();
7	
8// ------------------------------------------ //
9$("#BacktoTop").click(function () {
10scrollToAnchor('PageTop');
11});	
12// ------------------------------------------ //
13$(document).scroll(function() {
14scrollButton();
15});						
16// ------------------------------------------ //
17$(window).resize(function() {
18scrollButton();
19});				
20// ------------------------------------------ //
21function scrollToAnchor(aid) {
22var aTag = $("a[id='" + aid + "']");
23$('html,body').animate({
24scrollTop: aTag.offset().top
25}, 'slow');
26}
27// ------------------------------------------ //
28function scrollButton() {
29var vMinWidth = 1550;
30var vScrollTop = $(document).scrollTop();
31var vDocWidth = $(document).width();
32var vContainerWidth = $(".Container").width();
33var vButtonWidth = $("#BacktoTop").width();
34var vSpace = (vDocWidth - vContainerWidth) / 2;
35var vButtonX = (vSpace / 2) - (vButtonWidth * 1.25);
36var vButtonX = vButtonX + 'px';
37if (vDocWidth > vMinWidth) {
38if (vScrollTop > 0) {
39$("#BacktoTop").fadeIn(500);
40$("#BacktoTop").css('bottom','30px');
41$("#BacktoTop").css('right',vButtonX);
42} else {
43$("#BacktoTop").fadeOut(500);
44};
45} else {
46$("#BacktoTop").fadeOut(500);
47};	
48}
49// ------------------------------------------ //
50});