Export everything if no items are selected?

Hi - I have a table using HTML data and the jquery-datatables-checkboxes plugin to display some information I'd like to export. I know I could do something like an "Export all" and then an "Export selected" button, but ideally I'd like just one button that would export all the displayed rows if nothing is selected (and, of course, just the selected rows if there is a selection).

Hopefully that makes sense! I'd be glad to provide a debugger session if needed. Here's the code:

              var table = $('#member_table').DataTable({
                // l - length changing input control
                // f - filtering input
                // t - The table!
                // i - Table information summary
                // p - pagination control
                // r - processing display element
                'dom': 'fBrtip',
                'paging': false,
                'autoWidth': false,
                searchPane: {
                  columns: '.filterable',
                  threshold: 0
                },
                'stateSave': true,
                'stateDuration': 0,
                'buttons': [

                    {
                      text: '<i class="fa fa-plus"></i> Add to list',
                      className: 'btn btn-primary',
                      titleAttr: 'Add to list',
                      action: function ( e, dt, button, config ) {
                        window.location = '<%= [rails url] %>';
                      }
                    },
                  {
                    extend: 'selected',
                    text: '<i class="fa fa-edit"></i> Edit Multiple',
                    className: 'btn btn-info',
                    titleAttr: 'Edit Multiple',
                    action: function ( e, dt, button, config ) {
                      $('#edit_multiple_form').submit();
                    }
                  },
                  {
                    extend: 'colvis',
                    text: '<i class="fa fa-filter"></i> Show Columns',
                    className: 'btn btn-warning',
                    titleAttr: 'Select Columns'
                  },
                  {
                    extend: 'print',
                    text: '<i class="fa fa-print"></i>',
                    titleAttr: 'Print',
                    exportOptions: {
                      columns: ':visible :not(.sorting_disabled)'
                    }
                  },
                  {
                    extend: 'collection',
                    text: '<i class="fa fa-share"></i> Export',
                    buttons: [
                      {
                        extend: 'excelHtml5',
                        exportOptions: {
                          rows: { selected: true },
                          columns: ':visible :not(.sorting_disabled)'
                        }
                      },
                      {
                        extend: 'csvHtml5',
                        exportOptions: {
                          rows: { selected: true },
                          columns: ':visible :not(.sorting_disabled)'
                        }
                      }
                    ]
                  }
                ],

                'columnDefs': [
                  {
                    'targets': 0,
                    'checkboxes': {
                      'selectRow': true
                    }
                  }
                ],
                'select': {
                  'style': 'multi'
                },
                'order': [[1, 'asc']]
              });