How to check that the length of a string is equal to 0 in angular JS

1


I declared and initialized an array with various fields including targaauto. In the add function, I check "If the length of the car plate is equal to 0 I get an alert" Error! Insert the license plate! ". All this does not work correctly. In fact, if I do not enter the license plate I do not see the alert. I have tried the following conditions inside the if in addition to the one defined in the code

START CODE ANGULAR JS

angular.module('tabelle', [])
.controller('test', function($scope){


$scope.cars =    [{id: "1", targaauto : "AR152FP", datiintestatario : "Maurizio Generosi", 
                 marca : 
                 "FIAT PUNTO", id_bottone: "1"},
                 {id: "2", targaauto  : "AR34512", datiintestatario : "Nicola Lops", marca : 
                 "TOYOTA YARIS", id_bottone: "2"},
                 {id: "3", targaauto : "BS25671", datiintestatario : "Sabrina De Martino", 
                 marca 
                 : "FIAT PANDA", id_bottone: "3"}];

$scope.aggiungi = function() {
    if($scope.cars.targaauto.length==0){
        alert("Errore! Inserire la targa");
    }
    $scope.cars.push({
    id: $scope.id,
    targaauto: $scope.targaauto,
    datiintestatario: $scope.datiintestatario,
    marca: $scope.marca,
    id_bottone: $scope.id_bottone
    })


    $scope.id = " ";
    $scope.targaauto = " ";
    $scope.datiintestatario = " ";
    $scope.marca = " ";
};


$scope.rigadaeliminare = function(indice) {
$scope.idcancellare = indice;

};
$scope.rimuovi = function () {
$scope.cars.splice($scope.idcancellare, 1);
};

//SELEZIONE INDICE DELLA RIGA DEL RECORD
function rigadamodificare(indice){
for(let i=0; i<$scope.cars.length;i++){
    if($scope.cars[i].id==indice){
        return i;
    }
}
return -1;
};

$scope.aggiorna = function(id) {
let index = rigadamodificare(id);
let i = $scope.cars[index];
$scope.id=i.id;
$scope.targaauto=i.targaauto;
$scope.datiintestatario=i.datiintestatario;
$scope.marca=i.marca;
};

$scope.salva = function() {
let index = rigadamodificare($scope.id);
$scope.cars[index].targaauto = $scope.targaauto;
$scope.cars[index].datiintestatario = $scope.datiintestatario;
$scope.cars[index].marca = $scope.marca;

        $scope.id = " ";
        $scope.targaauto = " ";
        $scope.datiintestatario = " ";
        $scope.marca = " ";
};
});

PROVEN CONDITIONS

if (cars.targaauto.length == 0)

if ($ cars.targaauto.length == 0)

if (targaauto.length == 0)