$query_product=$this->db->query("SELECT item,item_sku  FROM `item` Where id IN (".implode(',',$res_data).")")->result();

exit(json_encode( array('query_product'=>$query_product)));

.done(function (res) {

//here i need to do something

      }
      $('#itemModal').modal('show');
})

{"query_product":"whatever_it_is"}

.done(function(res) {
    var result = res.query_product;
    //any extra manipulation
 }