Jquery Bind Table th td add && Remove

HTML TABLE

<table id="datagrid" style="width:100%">

  <tr id="thid">

  <thead>

    <th>Firstname</th>

    <th>Lastname</th> 

    <th>Age</th>

  </tr>

  </thead>

  <tbody>

  <tr>

    <td>Jill</td>

    <td>Smith</td>

    <td>50</td>

  </tr>

 </tbody>

</table>

JQUERY

Add th

 $("#datagrid>thead>tr").append('<th class="btn-success dynamicrow">Unit</th><th class="btn-success dynamicrow">Sub-Unit</th>'); 

OR
 $('#thid').append('<th style="font-size:12px;" class="btn-success dynamicrow">Unit</th><th style="font-size:12px;" class="btn-success dynamicrow">Sub-Unit</th>');

Remove th

 $('.dynamicrow').remove();