无法在codeigniter中向数据表添加EXPORT按钮

I have loaded the following necessary scrip and CSS in head. Here is my code

<script type="text/javascript" src="https://cdn.datatables.net/1.10.11/js/jquery.dataTables.min.js"></script>
<script type="text/javascript" src="https://cdn.datatables.net/buttons/1.1.2/js/dataTables.buttons.min.js"></script>
<script type="text/javascript" src="//cdn.datatables.net/buttons/1.1.2/js/buttons.flash.min.js"></script>
<script type="text/javascript" src="//cdnjs.cloudflare.com/ajax/libs/jszip/2.5.0/jszip.min.js"></script>
<script type="text/javascript" src="//cdn.rawgit.com/bpampuch/pdfmake/0.1.18/build/pdfmake.min.js"></script>
<script type="text/javascript" src="//cdn.rawgit.com/bpampuch/pdfmake/0.1.18/build/vfs_fonts.js"></script>
 <script type="text/javascript" src="//cdn.datatables.net/buttons/1.1.2/js/buttons.html5.min.js"></script>
<script type="text/javascript" src="//cdn.datatables.net/buttons/1.1.2/js/buttons.print.min.js"></script>

CSS code:

<link rel="stylesheet" href="https://cdn.datatables.net/1.10.11/css/jquery.dataTables.min.css">
<link rel="stylesheet" href="https://cdn.datatables.net/buttons/1.1.2/css/buttons.dataTables.min.css">

Here is my datatable code. Through DOM it is only changing position of search and showing entries per page but I am not getting the various export buttons.

$(document).ready(function() {
table = $('#table').DataTable({ 
      "dom": '<"top"i>rt<"bottom"flp><"clear">',
    "buttons": [
        'copy', 'csv', 'excel', 'pdf', 'print'
    ],
    "processing": true, //Feature control the processing indicator.
    "serverSide": true, //Feature control DataTables' server-side processing mode.
    "order": [], //Initial no order.

    // Load data for the table's content from an Ajax source
    "ajax": {
        "url": "<?php echo site_url('person/ajax_list')?>",
        "type": "POST"
    },

    //Set column definition initialisation properties.
    "columnDefs": [
    { 
        "targets": [ -1 ], //last column
        "orderable": false, //set not orderable
    },
    ],

});

//datepicker
$('.datepicker').datepicker({
    autoclose: true,
    format: "yyyy-mm-dd",
    todayHighlight: true,
    orientation: "top auto",
    todayBtn: true,
    todayHighlight: true,  
});

//set input/textarea/select event when change value, remove class error and remove text help block 
$("input").change(function(){
    $(this).parent().parent().removeClass('has-error');
    $(this).next().empty();
});
$("textarea").change(function(){
    $(this).parent().parent().removeClass('has-error');
    $(this).next().empty();
});
$("select").change(function(){
    $(this).parent().parent().removeClass('has-error');
    $(this).next().empty();
});
});

You should have a 'B' in your "dom" property :

"dom": 'B<"top"i>rt<"bottom"flp><"clear">'

That's what trigger the creation of the buttons