You don't have any option with value 4
if($('select[name="number"]').val() == '4'){
change it to
if($('select[name="number"]').val() == '2'){
Problem
<option value="2">4</option>
// ^ value is 2 not 4
Or
If you want to do it with text of option
if ($('select[name="number"] option:selected').text() == '4')