this is select box html
<select name="selectBox" id="selectBox">
<option value="option1">option1</option>
<option value="option2">option2</option>
<option value="option3">option3</option>
<option value="option4">option4</option>
</select>
when you want to totally remove and add option from select box then you can use this code
$("#selectBox option[value='option1']").remove();
$("#selectBox").append('<option value="option1">Option</option>');
sometime we need to hide and show option from select box , but not remove then you can use this code
$("#selectBox option[value='option1']").hide();
$("#selectBox option[value='option1']").show();
sometime need to remove selected option from select box then
$('#selectBox :selected').remove();
$("#selectBox option:selected").remove();
when you need to remove all option then this code
('#selectBox').empty();
when need to first option or last then this code
$('#selectBox').find('option:first').remove();
$('#selectBox').find('option:last').remove();