"

From 2014.igem.org

$(document).ready(function (){ var stats = $('.back-to-top'), timer;

       var offset = 220;

stats.hide();

$(function () { $(window).scroll(function() {

 if (jQuery(this).scrollTop() > offset) {
           stats.fadeIn();
           clearTimeout(timer);  
           timer = setTimeout(function() {

stats.stop(true,true).fadeOut('slow'); }, 3000);

   }

});

$('.back-to-top').click(function () { $('body,html').animate({ scrollTop: 0 }, 800); return false; }); }); });

jQuery(window).scroll(function() {
       if ((this).scrollTop() > offset) {
           ('.back-to-top').fadeIn(duration);       
   }