how to add new row in table on button click in javascript with next number code example

Example: how to add new row in table on button click in javascript with next number

<table id="tbl">
    <tr>
        <td><input type="text" name="links" /></td>
        <td><input type="text" name="keywords" /></td> 
        <td><input type="text" name="violationtype" /></td>   
        <td><input type="submit" class="button" value="Add another line" onclick="addField(this);" /></td>          
    </tr>
</table>