button style in jquery datatable

1$(document).ready(function() {
2    $('#example').DataTable( {
3        dom: 'Bfrtip',
4        buttons: [
5            {
6                extend:    'copyHtml5',
7                text:      '<i class="fa fa-files-o"></i>',
8                titleAttr: 'Copy'
9            },
10            {
11                extend:    'excelHtml5',
12                text:      '<i class="fa fa-file-excel-o"></i>',
13                titleAttr: 'Excel'
14            },
15            {
16                extend:    'csvHtml5',
17                text:      '<i class="fa fa-file-text-o"></i>',
18                titleAttr: 'CSV'
19            },
20            {
21                extend:    'pdfHtml5',
22                text:      '<i class="fa fa-file-pdf-o"></i>',
23                titleAttr: 'PDF'
24            }
25        ]
26    } );
27} );
28