https://www.officialcatholicdirectory.com/assets/directives/web.window.scroll.directive.js

1angular.module('web')
2    .directive("scroll", function($window) {
3        return function(scope, element, attrs) {
4            angular.element($window).bind("scroll", function() {
5                var scrollPos = angular.element($window).scrollTop();
6                var navItem = angular.element('#navbar a.page-scroll');
7
8                if (angular.element($window).scrollTop() > 150) {
9                    angular.element('#back_to_top').fadeIn();
10                } else {
11                    angular.element('#back_to_top').fadeOut();
12                }
13
14                angular.element('#navbar a.page-scroll').each(function() {
15                    var currLink = angular.element(this);
16                    var currHash = angular.element(this).attr('href');
17                    if (currHash && currHash.indexOf('/') == -1) {
18                        var refElement = angular.element(currHash);
19                        if (refElement.length) {
20                            if (refElement.offset().top <= scrollPos && refElement.offset().top + refElement.height() > scrollPos) {
21                                angular.element('#navbar ul li').removeClass("active");
22                                angular.element(currLink).parent('li').addClass("active");
23                            } else {
24                                angular.element(currLink).parent('li').removeClass("active");
25                            }
26                        }
27                    }
28
29
30
31                });
32                scope.$apply();
33            });
34        };
35    });