Using angular and Ionic, how do I traverse a vector by summing a variable of an object?

Question

I have a vector of objects with prices, product name..., after the customer has clicked on a product I pass it to another list, of orders, after being done this need to make me add up the prices of the products of the list and return me a total each time q a new product is added and if removed needs to be subtracted from the total. I’m using $Scope in this application because it’s an Ionic app.

I’m using a service to fill this list because I have two more vectors q have the msm specifications but divide the products into two more vectors to better organize and it was the solution I found. But I don’t understand what it represents very well in the code.

.controller('pedidoCtrl', function($scope, produtoService) {

    $scope.items = [];
    $scope.items = produtoService.getProdutos();

    $scope.deleteItem = function(item){
        $scope.items.splice($scope.items.indexOf(item), 1);
    };
})

.service('produtoService', [function(){
    var produtosLista = [];

    var addProduto = function(produto) {
        produtosLista.push(produto);
    };

    var getProdutos = function(){
        return produtosLista;
    };

    return {
        addProduto: addProduto,
        getProdutos: getProdutos,
    };
}]);