How to Dynamically Manage View-Specific Stylesheets in AngularJS?

How to Include View-Specific Styling in AngularJS

Properly managing stylesheets for various views is essential in an AngularJS application. Traditionally, this was done by placing elements directly within the HTML of each view. However, this approach is considered poor practice despite browser support, as it can lead to performance issues and maintainability challenges.

Preferred Approach

A preferred method is to dynamically load stylesheets only when a specific view is navigated to. This ensures optimal performance and prevents flashes of unstyled content. Here's how you can achieve this:

1. Create a Custom Directive for Element

This directive will be responsible for dynamically adding and removing page-specific elements to the section.

app.directive('head', ['$rootScope', '$compile', function($rootScope, $compile){
  return {
    restrict: 'E',
    link: function(scope, elem){
      var html = '<link rel="stylesheet" ng-repeat="(routeCtrl, cssUrl) in routeStyles" ng-href="{{cssUrl}}" />';
      elem.append($compile(html)(scope));
      scope.routeStyles = {};
      $rootScope.$on('$routeChangeStart', function (e, next, current) {
        if(current && current.$$route && current.$$route.css){
          if(!angular.isArray(current.$$route.css)){
            current.$$route.css = [current.$$route.css];
          }
          angular.forEach(current.$$route.css, function(sheet){
            delete scope.routeStyles[sheet];
          });
        }
        if(next && next.$$route && next.$$route.css){
          if(!angular.isArray(next.$$route.css)){
            next.$$route.css = [next.$$route.css];
          }
          angular.forEach(next.$$route.css, function(sheet){
            scope.routeStyles[sheet] = sheet;
          });
        }
      });
    }
  };
}]);

2. Specify Stylesheet Association in $routeProvider

This involves adding a css property to each route configuration object. The value can be a single string representing the stylesheet path or an array of strings for multiple stylesheets.

app.config(['$routeProvider', function($routeProvider){
  $routeProvider
    .when('/some/route/1', {
      templateUrl: 'partials/partial1.html', 
      controller: 'Partial1Ctrl',
      css: 'css/partial1.css'
    })
    .when('/some/route/2', {
      templateUrl: 'partials/partial2.html',
      controller: 'Partial2Ctrl'
    })
    .when('/some/route/3', {
      templateUrl: 'partials/partial3.html',
      controller: 'Partial3Ctrl',
      css: ['css/partial3_1.css','css/partial3_2.css']
    })
}]);

This setup will dynamically load the designated stylesheets into the element only when the corresponding views are navigated to, ensuring optimal performance and a consistent user experience.

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