使用动态选择进行验证，基于laravel，jquery和ajax的另一个选择

I need some help with Laravel, PHP, jquery and ajax!

I have a employee registration page. The salary is dynamically filled when the employee occupation is selected, with jquery and ajax.

I need to validate before the post with jquery in this case?

I make the validation in back-end with laravel validation. When i have a validation error and returns from controller to view, i can't set selected salary before.

$.get('/ajax-salarios?id_cargo=' + id_cargo, function (data) {
        //success data
        if (data.length > 0) {
            $('#salario').empty();
            document.getElementById('salario').disabled = false;
            $('#salario').append('<option value="">Selecione...</option>');
            $.each(data, function (index, salariosObj) {
                $('#salario').append('' +
                    '<option value="' + salariosObj.id + '">' + salariosObj.salario + '</option>' +
                    '');
            });
        } else {
            $('#salario').empty();
            $('#salario').append('<option value="">Selecione...</option>');
            document.getElementById('salario').disabled = true;
        }
    });