https://www.imai-miki.net/js/jquery.pagescroller.js

1/*
2 * jQuery Page Scroller 1.0.0
3 *
4 * Requirements
5 * jQuery version 1.7 or higher
6 */
7(function($) {
8	$.fn.extend({
9		"pageScroller" : function() {
10			var _this = this;
11			$(document).on('click', _this.selector, function() {
12				var target = $(this).attr('href');
13				if(target.match(/^#.+/)) {
14					$('html,body').animate(
15						{ scrollTop: $(target).offset().top},
16						{"easing" : "easeOutCubic"}
17					);
18					return false;
19				}
20			});
21			
22			return this;
23		}
24	});
25	$.extend(
26		jQuery.easing, {
27		"easeOutCubic": function (x, t, b, c, d) {
28			return c*((t=t/d-1)*t*t + 1) + b;
29		}
30	});
31})(jQuery);