如何比较angularjs中datepicker中的2个日期

Question

我正在尝试比较酒店登记和结账的2个日期，我使用bootstrap UI DatePicker，但由于某些原因我的代码对我不起作用，请指出我的代码有什么问题？感谢

$scope.$watch('lodging.checkIn',function(newVal,oldVal){
                var checkinDate = new Date(newVal);
                var checkoutDate = new Date($scope.lodging.checkOut);
                    if(checkinDate < checkoutDate){
                            $scope.lodging.lastNightBilled = false;
                            $scope.disableLastNight = false;
                          }else if(checkinDate == checkoutDate){
                            $scope.lodging.lastNightBilled = true;
                            $scope.disableLastNight = true;
                          }else{
                             $scope.lodging.lastNightBilled = false;
                             $scope.disableLastNight = false;
                      }
        });
        $scope.$watch('lodging.checkOut',function(newVal,oldVal){
                 var checkinDate = new Date($scope.lodging.checkIn);
                 var checkoutDate = new Date(newVal);
                    if(checkinDate < checkoutDate){
                            $scope.lodging.lastNightBilled = false;
                            $scope.disableLastNight = false;
                          }else if(checkinDate == checkoutDate){
                            $scope.lodging.lastNightBilled = true;
                            $scope.disableLastNight = true;
                          }else{
                             $scope.lodging.lastNightBilled = false;
                             $scope.disableLastNight = false;
                      }
        });

HTML：

<div class="datebox">
                    <input type="text" show-button-bar='false'
                      class="form-control biginput" datepicker-popup
                      ng-model="lodging.checkIn" is-open="checkin" 
                      ng-required="true" close-text="Close" 
                      />

                    <span class="dateicon" style='right:5px;' ng-click="openCheckIn($event)"></span> 
                  </div>
                  <label class='ecom-label'>Check-In Date*</label><span ng-show='isCheckOutValid' class='floatright checkedicon'></span>
                </div>
                <div class="col-a datefloat" >
                  <div class="datebox">
                    <input type="text" show-button-bar='false'
                      class="form-control biginput" datepicker-popup 
                      ng-model="lodging.checkOut" is-open="checkout" min-date='lodging.checkIn'
                      ng-required="true"
                      close-text="Close" />
                    <span class="dateicon" style='right:5px;' ng-click="openCheckOut($event)"></span>
                  </div>

我做了一些断点，发现它总是忽略比较条件，结果总是：

$ scope.lodging.lastNightBilled = false;   $ scope.disableLastNight = false;

任何理想？