How to check if data already exists in the bank before inserting another in angular?

I have already made a modal that receives a name, it sends the controller in the function of inserting new contact. I want to check if this data is already registered in the bank so they do not sign it again. Anyone know how I can do this in AngularJS?

I've done this so far ...

//Carrega as categorias existentes

 var carregaCategorias = function(){
            var tam = $scope.categoria.length;
            for (var i = 0; i < tam; i++)
                $scope.categorias[i] = $scope.categoria[i].nome;
        }

//Verifica se já está inserido

$scope.createCategory = function(typeOfCategory, modalId){ //OK

            var typeCategory;
            var category = $scope.novaCategoria;

            if(category == ?? )