code: function (e) {
              var el = $(e.target);
              var date = moment(el.val(), this.format);
              if (!date.isValid()) return;
  
              var startDate, endDate;
              if (el.attr('name') === 'daterangepicker_start') {
                  startDate = date;
                  endDate = this.endDate;
              } else {
                  startDate = this.startDate;
                  endDate = date;
              }
              this.setCustomDates(startDate, endDate);
          }
docs: when a date is typed into the start to end date textboxes