Datatable row

HTML

<link rel="stylesheet" href="https://cdn.datatables.net/1.10.7/css/jquery.dataTables.css">
<script src="https://code.jquery.com/jquery-1.11.1.min.js"></script>
<script src="https://cdn.datatables.net/1.10.7/js/jquery.dataTables.min.js"></script>
<table id="example" class="display" cellspacing="0" width="100%">
    <thead>
        <tr>
            <th>Name</th>
            <th>Position</th>
            <th>Office</th>
            <th>Age</th>
            <th>Start date</th>
            <th>Salary</th>
        </tr>
    </thead>
    <tfoot>
        <tr>
            <th>Name</th>
            <th>Position</th>
            <th>Office</th>
            <th>Age</th>
            <th>Start date</th>
            <th>Salary</th>
        </tr>
    </tfoot>
    <tbody>
        <tr>
            <td>Tiger Nixon</td>
            <td>System Architect</td>
            <td>Edinburgh</td>
            <td>61</td>
            <td>2011/04/25</td>
            <td>$320,800</td>
        </tr>
        <tr>
            <td>Garrett Winters</td>
            <td>Accountant</td>
            <td>Tokyo</td>
            <td>63</td>
            <td>2011/07/25</td>
            <td>$170,750</td>
        </tr>
        <tr>
            <td>Ashton Cox</td>
            <td>Junior Technical Author</td>
            <td>San Francisco</td>
            <td>66</td>
            <td>2009/01/12</td>
            <td>$86,000</td>
        </tr>
        <tr>
            <td>Bradley Greer</td>
            <td>Software Engineer</td>
            <td>London</td>
            <td>41</td>
            <td>2012/10/13</td>
            <td>$132,000</td>
        </tr>
        <tr>
            <td>Dai Rios</td>
            <td>Personnel Lead</td>
            <td>Edinburgh</td>
            <td>35</td>
            <td>2012/09/26</td>
            <td>$217,500</td>
        </tr>
        <tr>
            <td>Jenette Caldwell</td>
            <td>Development Lead</td>
            <td>New York</td>
            <td>30</td>
           ...

JavaScript

$(document).ready(function () {
    var table=$('#example').dataTable({"pageLength": 8});
    
    $('#GetPageSizeBtn').click(function() {
        var tbl = $('#example').DataTable();
        var elements = $('#example tbody tr').size();
        alert("Current Page Size is: " + tbl.page.info().length + " Table shows " + elements + " elements");
    });    
});