AngularJS approach to binding window scroll

Hey there, I'm a newcomer to AngularJS with a background in jQuery. I'm trying to create a fixed-top navbar using AngularJS that has a background which changes from transparent to opaque as the window is scrolled. Unfortunately, I'm struggling to connect the window scroll event to the $scope variable.

This is what I've come up with so far, but it's not working properly:

Check out my code on JSFiddle

function bgScroll($scope) {
  angular.element(window).bind('scroll', function () {
    $scope.scroll = window.pageYOffset;
    $scope.height = document.getElementById('main-header').offsetHeight;
    $scope.a = $scope.scroll / $scope.height;
    $scope.bgColor = 'rgba(0,0,0,' + $scope.a + ')';
  });
}

Here's how it looks on the view side:

<div ng-controller="bgScroll">
  <nav class="navbar navbar-inverse navbar-bw navbar-fixed-top" role="navigation" style="background-color: {{ bgColor }};">
    ...
  </nav>
</div>

I would really appreciate any assistance or suggestions you can provide! Thanks in advance.

javascriptangularjs

Answer №1

angular.element makes use of jQuery (if it's added) or JQlite to handle callback functions, which means that updates to your $scope won't happen automatically.

function changeColorOnScroll($scope) {
  angular.element(window).bind('scroll', function () {
    $scope.scroll = window.pageYOffset;
    $scope.height = document.getElementById('main-header').offsetHeight;
    $scope.opacity = $scope.scroll / $scope.height;
    $scope.bgColor = 'rgba(0,0,0,' + $scope.opacity + ')';

    // Make sure to update the scope manually
    $scope.$apply();
  });
}

Answer №2

A better approach is to refrain from performing DOM manipulation in the controller. It's recommended to create a new directive and handle it there.

enter code here

<div custom-scroll ng-controller="customScroll">
  <nav class="navbar navbar-inverse navbar-bw navbar-fixed-top" role="navigation" style="background-color: {{ navColor }};">
    ...
  </nav>
</div>   
myApp.directive('customScroll', function () {
    return {
        restrict: 'A',
        link: function (scope, element, attrs) {
            angular.element(window).bind('scroll', function () {
               scope.scrollPosition = window.pageYOffset;
               scope.headerHeight = document.getElementById('main-header').offsetHeight;
               scope.opacityValue = scope.scrollPosition / scope.headerHeight;
               scope.navColor = 'rgba(0,0,0,' + scope.opacityValue + ')';
            });
scope.$on('$destroy', function() {
        angular.element(window).unbind('scroll');
      });
        }
    };
});

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