jQuery Error: Cannot read property length of undefined in ASP.Net

this error appear and i dont know hot to fix :

Cannot read property 'length' of undefined

$(document).ready(function () {
    var table = $('#TLBCampaing').DataTable({
        'ajax': {

            type: "POST",
            dataType: "json",
            url: "/Admin/GetAllCampainsActive"
        },
        'columnDefs': [
           {
               'targets': 0,
               'checkboxes': {
                   'selectRow': true
               }
           }
        ],
        'select': {
            'style': 'multi'
        },
        'order': [[1, 'asc']]
    });


    // Handle form submission event 
    $('#frm-example').on('submit', function (e) {
        var form = this;

        var rows_selected = table.column(0).checkboxes.selected();

        // Iterate over all selected checkboxes
        $.each(rows_selected, function (index, rowId) {
            // Create a hidden element 
            $(form).append(
                $('<input>')
                   .attr('type', 'hidden')
                   .attr('name', 'id[]')
                   .val(rowId)
            );
        });
    });
})

can someone help me plz