https://colobu.com/js/totop.js

1(function($) {
2	// When to show the scroll link
3	// higher number = scroll link appears further down the page
4	var upperLimit = 800;
5	// Our scroll link element
6	var scrollElem = $('#totop');
7	// Scroll to top speed
8	var scrollSpeed = 500;
9	// Show and hide the scroll to top link based on scroll position
10	scrollElem.hide();
11	$(window).scroll(function () {
12		var scrollTop = $(document).scrollTop();
13		if ( scrollTop > upperLimit ) {
14			$(scrollElem).stop().fadeTo(300, 1); // fade back in
15		}else{
16			$(scrollElem).stop().fadeTo(300, 0); // fade out
17		}
18	});
19	// Scroll to top animation on click
20	$(scrollElem).click(function(){
21		$('html, body').animate({scrollTop:0}, scrollSpeed); 
22		return false;
23	});
24})(jQuery);