Detect unsaved changes and alert user using angularjs

Question

Below is the code so far

Answer 1

I've extended the @Anders answer to clean up listeners (unbind listers) when directive is destroyed (ex: when route changes), and added some syntactic sugar to generalise the usage.

confirmOnExit Directive:

/**
 * @name confirmOnExit
 * 
 * @description
 * Prompts user while he navigating away from the current route (or, as long as this directive 
 * is not destroyed) if any unsaved form changes present.
 * 
 * @element Attribute
 * @scope
 * @param confirmOnExit Scope function which will be called on window refresh/close or AngularS $route change to
 *                          decide whether to display the prompt or not.
 * @param confirmMessageWindow Custom message to display before browser refresh or closed.
 * @param confirmMessageRoute Custom message to display before navigating to other route.
 * @param confirmMessage Custom message to display when above specific message is not set.
 * 
 * @example
 * Usage:
 * Example Controller: (using controllerAs syntax in this example)
 * 
 *      angular.module('AppModule', []).controller('pageCtrl', [function () {
 *          this.isDirty = function () {
 *              // do your logic and return 'true' to display the prompt, or 'false' otherwise.
 *              return true;
 *          };
 *      }]);
 * 
 * Template:
 * 
 *      

 * 
 * @see
 * http://stackoverflow.com/a/28905954/340290
 * 
 * @author Manikanta G
 */
ngxDirectivesModule.directive('confirmOnExit', function() {
    return {
        scope: {
            confirmOnExit: '&',
            confirmMessageWindow: '@',
            confirmMessageRoute: '@',
            confirmMessage: '@'
        },
        link: function($scope, elem, attrs) {
            window.onbeforeunload = function(){
                if ($scope.confirmOnExit()) {
                    return $scope.confirmMessageWindow || $scope.confirmMessage;
                }
            }
            var $locationChangeStartUnbind = $scope.$on('$locationChangeStart', function(event, next, current) {
                if ($scope.confirmOnExit()) {
                    if(! confirm($scope.confirmMessageRoute || $scope.confirmMessage)) {
                        event.preventDefault();
                    }
                }
            });

            $scope.$on('$destroy', function() {
                window.onbeforeunload = null;
                $locationChangeStartUnbind();
            });
        }
    };
});

Usage: Example Controller: (using controllerAs syntax in this example)

angular.module('AppModule', []).controller('pageCtrl', [function () {
    this.isDirty = function () {
        // do your logic and return 'true' to display the prompt, or 'false' otherwise.

        return true;
    };
}]);

Template: