jquery มีปัญหา เรื่อง select option undefined ครับ

$('#save_user').on('click', function(){


var depart =  $("#dep option:selected" ).val();
var jobs =  $("#job option:selected" ).val();




form_user = $("#user_add").serialize();

var base_url = '<?php echo base_url()?>';


$.ajax({
url:base_url + 'c_user/insertUser',
data:form_user +"&depart=" + depart + "&jobs=" + jobs ,
cache:false,
type:'post',
success: function(user){


if(user !== ''){
alert(user);
$('#add_res').html("<span class=\"label label-warning\">" + user + "</span>");

}


else{

$('.result').html("<span class=\"label label-warning\">" + 'no data' + "</span>"); 

}
},
error:function(){
//when return false

alert(depart);

}
});
});

$.ajax({

url:base_url + 'c_category/departList',
data:'',
dataType: "text",
cache:false,
type:'post',
success: function(dep){

if(dep !== ''){
var re = $.parseJSON(dep);
var count = dep.length;               
var i = 0;

for(i=0;i<count;i++){
$.each(re ,function(index,value)
 {
  
$("#dep").append("<option value="+value[i].DepCod+">"+value[i].DepLocNam+"</option>"); ///// บรรทัดนี้ครับที่ error 
           
});
}
}
else{
$('.dep').html("no data"); 

}
},
error:function(){
$('.dep').html("no data"); 
}
});