javascript - validate mulitiple date fields -

i'm creating form have datepicker , timepicker both starting date , ending date. in total got 4 fields. able validate if startdate (a combination of startdate , starttime) earliere enddate. can't seem figure out , how should put validation.

so whenever 1 of fields edited should trigger validation.

i can't seem figure out , how create validation, i've tried create custom validation named method-validation retrieve method controller decided if validation propper, can't put on 1 field, because if change other field validation not triggered.

anyone have idear working ?

bottom line is, want able take 2 , 2 fields set them togehter, , compare them, , show message if end smaller start.

follow up:

the issue isn't comparing 2 dates. can achieve.

<input type="text" ng-model="activity.startdate" date-picker> <input type="text" ng-model="activity.starttime" time-picker>  <input type="text" ng-model="activity.enddate" date-picker> <input type="text" ng-model="activity.endtime" time-picker> 

it making sure combination of 2 field isn't off

module.directive('validdate', function(){     return {         require: 'ngmodel',         link: function(scope, elm, attrs, ctrl) {             function  validator(value){                 var valid = true;                 if (value != undefined) {                   value = moment(value, 'yyyy-mm-dd').format('yyyy-mm-dd');                    if (((attrs.validdate == 'start') && (value >= scope.$eval(attrs.otherdate))) || ((attrs.validdate == 'end') && ((value < scope.$eval(attrs.otherdate))))) {                     valid = false;                   }                                          } else {                    valid = false;                  }                  ctrl.$setvalidity('date-valid', valid);                  return value;             }              scope.$watch([attrs.otherdate, attrs.ngmodel] ,function(newvalue) {                 validator(scope.$eval(attrs.ngmodel));                 }, true);                                 }     }; }); 

usage:

<input type="date" ng-model="startdate" valid-date="start" other-date="enddate" /> <input type="date" ng-model="enddate" valid-date="end" other-date="startdate" /> 

let me know if works. used momentjs library formatting here feel free change it.