동적으로 select option 추가 하기(empty와 append) 채택완료

<div class="form-group has-feedback text-gap">			<label class="col-sm-2 control-label" for="reg_mb_1"><b>분야</b><strong class="sound_only">필수</strong></label>			<div class="col-sm-3">                <select name="mb_1" id="reg_mb_1" required class="form-control input-sm nospace" onchange="itemChange()">                    <option value="">선택하세요</option>					<option value="A" <?php echo get_selected($member['mb_1'],"A");?>>A</option>					<option value="B" <?php echo get_selected($member['mb_1'],"B");?>>B</option>					<option value="C" <?php echo get_selected($member['mb_1'],"C");?>>C</option>                </select>			</div>			</div>						<div class="form-group has-feedback text-gap">			<label class="col-sm-2 control-label" for="reg_mb_2"><b>2차 분야</b><strong class="sound_only">필수</strong></label>			<div class="col-sm-3">                <select name="mb_2" id="reg_mb_2" class="form-control input-sm nospace">				 <option value="">선택하세요</option>                </select>			</div>			</div><script>function itemChange(){ var keyboard = ["갈축","청축","적축"];var mouse = ["광마우스","유선마우스","비싼마우스","미키마우스"];var monitor = ["17인치","22인치","24인치","26인치"]; var selectItem = $("#reg_mb_1").val(); var changeItem;  if(selectItem == "A"){  changeItem = keyboard;}else if(selectItem == "B"){  changeItem = mouse;}else if(selectItem == "C"){  changeItem =  monitor;} $('#reg_mb_2').empty(); for(var count = 0; count < changeItem.size(); count++){                                var option = $("<option>"+changeItem[count]+"</option>");                $('#reg_mb_2').append(option);            } } </script>