Angular.JS Uncaught TypeError: Cannot assign to read only property

Question

Trying to create an app, with a toggle setting that should be saved to local storage, haven't gotten much luck with it, though.

I'm using Ionic + Angular.JS

Here's my code, I'm getting the error Uncaught TypeError: Cannot assign to read only property

Controller.js:

.controller("ExampleController", ['$scope', '$window', function($scope, $window) { 


    $scope.CONFIG = localStorage.getItem('CONFIG');
        if (!$scope.CONFIG) {
          $scope.CONFIG = {karton: true};
        }

        $scope.save = function(checked) {
          $scope.CONFIG.karton = checked;
          localStorage.setItem('CONFIG', $scope.CONFIG);
        }

}]);

the HTML file:

<div  class="item item-avatar item-icon-right">
       <img src="img/box.jpg"> 
       <ion-toggle type="checkbox" ng-model="karton.checked" ng-change="save(karton.checked)" ng-init="karton.checked = CONFIG.karton" toggle-class="toggle-balanced" id="karton" name="karton">Karton</ion-toggle>
       <div>Box Value: <span class="val">{{karton }}</span></div>
</div>

EDIT

I now have this but it returns an "undefined" in the console log:

.controller("ExampleController", ['$scope', '$window', function($scope, $window) { 
    $scope.CONFIG = (localStorage.getItem('CONFIG'));
        if (!$scope.CONFIG) {
          $scope.CONFIG = {karton: true};

        }
        $scope.save = function(checked) {
          JSON.stringify($scope.CONFIG.karton) === checked;
          localStorage.setItem('CONFIG', JSON.stringify($scope.CONFIG));
          console.log(JSON.stringify($scope.CONFIG.karton));
        }
}]);

Answer 1

The value of $scope.CONFIG is an object, localStorage only supports strings. Use JSON.stringify() and JSON.parse().

.controller("ExampleController", ['$scope', '$window', function($scope, $window) { 
    $scope.CONFIG = JSON.parse(localStorage.getItem('CONFIG'));
        if (!$scope.CONFIG) {
          $scope.CONFIG = {karton: true};
        }
        $scope.save = function(checked) {
          $scope.CONFIG.karton = checked;
          localStorage.setItem('CONFIG', JSON.stringify($scope.CONFIG));
        }
}]);