The variable in the scope of AngularJS is showing as "undefined

Hello everyone, I'm facing some challenges with AngularJS. I've spent the entire day trying to solve this issue but as a beginner, I'm really stuck and hoping for some assistance. The error I'm encountering is 'Cannot read property 'length' of undefined'. In my program, I have an array of objects called '$scope.products' sourced from a .json file. I am filtering this array to display only products under the category 'special offers'.

$scope.specialOffers = $filter('filter')($scope.products,{category:"Special 
Offers"}, true);

After filtering, I want to determine the length of this new array and use it in my randomInt function to generate a random integer between 0 and the length of the array. However, the '$scope.specialOffers' variable is showing up as undefined for some reason. Here is my complete controller code:

app.controller('ProductsController', ['$scope','$filter', 'productFactory', 
'$location', '$routeParams', 
function ($scope, $filter, productFactory, $location, $routeParams) {

$scope.path;
$scope.category;
$scope.products;
$scope.rand;
$scope.specialOffers;
$scope.id = $routeParams.id;

specifyCategory();
getProducts();

$scope.specialOffers = $filter('filter')($scope.products,{category:"Special Offers"}, true);

$scope.rand = randomInt($scope.specialOffers.length, 0);

function specifyCategory() {
    $scope.path = $location.path();
    if ($scope.path == "/products/woodentoys") {
        $scope.category = "Wooden Toys"
    } else if ($scope.path == "/products/woodenaccessories") {
        $scope.category = "Wooden Accessories"
    } else if ($scope.path == "/products/specialoffers"){
        $scope.category = "Special Offers"
    }
}

function getProducts() {
    productFactory.getProducts()
        .then(function (response) {
            $scope.products = response.data;

        }, function (error) {
            $scope.status = 'unable to load product data ' + error.message;
        });
}

function randomInt(max,min){
    max++;
    return Math.floor((Math.random())*(max-min))+min;
}

}]);

This is my first time asking a question on Stack Overflow, so your patience is greatly appreciated. Thank you in advance!

Answer №1

It seems that the error message is not visible, but my initial assumption is that $scope.products is being filtered before it gets properly assigned. The getProducts function likely returns an asynchronous promise:

function getProducts() {
    productFactory.getProducts()
        .then(function (response) {
           $scope.products = response.data;

        }, function (error) {
           $scope.status = 'unable to load product data ' + error.message;
    });
}

If you haven't already, try moving your data access logic inside the success callback function.

function getProducts() {
    productFactory.getProducts()
        .then(function (response) {
            $scope.products = response.data;
            $scope.specialOffers = $filter('filter')($scope.products, {category:"Special Offers"}, true);
            $scope.rand = randomInt($scope.specialOffers.length, 0);
        }, function (error) {
            $scope.status = 'unable to load product data ' + error.message;
        });
}

Answer №2

The reason for this issue is that the products request is taking longer than expected to complete. This causes $scope.products to be accessed before the request has finished, resulting in it displaying as undefined.

To resolve this, consider applying your filter within the callback function of the request or explore the option of using $watch.

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