javascript - 页面加载时发生空请求时如何防止 500 GET 错误？

Question

我有一个带有依赖下拉列表的表单，每当提交表单时都会加载该下拉列表，以便在表单提交之前选择的主要选择在提交后再次预加载。我注意到每当页面首次加载而没有传递参数时，我都会收到 GET: 500 Internal Server Error ，错误如下所示:

Internal Server Error: /operations/ajax/load-stations/

ValueError at /operations/ajax/load-stations/ invalid literal for int() with base 10: ''


Request URL: http://localhost:8000/operations/ajax/load-stations/?work_area=
Request Method: GET
Status Code: 500 Internal Server Error

因为当页面首次加载并且尚未提交任何表单时，work_area 为空(work_area = "")。如何修改 JS 或函数以避免出现此错误？

enter_exit.html

{% block main %}
    <form id="warehouseForm" action="" method="POST" data-stations-url="{% url 'operations:ajax_load_stations' %}" novalidate >
        {% csrf_token %}

        <div>
            <div>
                <label>Employee #</label>
                {{ form.employee_number }}

            </div>

            <div>
                <label>Work Area</label>
                {{ form.work_area }}
            </div>
            <div id="my-hidden-div">
                <label>Station</label>
                {{ form.station_number }}
            </div>
<!-- Rest of the form -->
        </div>

    </form>

    <script>
        function loadStations() {
            var url = $("#warehouseForm").attr("data-stations-url");
            var workAreaId = $(this).val();
            var $stationNumberField = $("#{{ form.station_number.id_for_label }}");

            $.ajax({
                url: url,
                data: {
                    'work_area': workAreaId
                },
                success: function (data) {
                    $("#my-hidden-div").show(); // show it
                    $stationNumberField.html(data);
                    // Check the length of the options child elements of the select
                    if ($stationNumberField.find("option").length === 1) {
                        $stationNumberField.parent().hide(); // Hide parent of the select node
                    } else {
                        // If any option, ensure the select is shown
                        $stationNumberField.parent().show();
                    }
                }
            });
        }
        $("#id_work_area").change(loadStations);
        $("#id_work_area").change();
     </script>

{% endblock main %}

views.py

def load_stations(request):
    work_area_id = request.GET.get('work_area')
    stations = Station.objects.filter(work_area_id=work_area_id).order_by('name')
    return render(request, 'operations/station_number_dropdown_options.html', {'stations': stations})

urls.py

urlpatterns = [
    url(r'enter-exit-area/$', views.enter_exit_area, name='enter_exit_area'),

    url(r'ajax/load-stations/$', views.load_stations, name='ajax_load_stations'),
]

Answer 1

最简单的方法是在启动 AJAX 请求之前测试 work_area 的值:

 if (workAreaId !== "") {
        $.ajax({
            url: url,
            data: {
                'work_area': workAreaId
            },
            success: function (data) {
                $("#my-hidden-div").show(); // show it
                $stationNumberField.html(data);
                // Check the length of the options child elements of the select
                if ($stationNumberField.find("option").length === 1) {
                    $stationNumberField.parent().hide(); // Hide parent of the select node
                } else {
                    // If any option, ensure the select is shown
                    $stationNumberField.parent().show();
                }
            }
        });
}