ngModelController demo

demo.js

angular
  .module('App', ['ngMessages'])
  .controller('AppController', ($scope) => {
    $scope.date = moment();
  })
  .directive('dateDigits', () => ({
    restrict: 'A',
    require: 'ngModel',
    link: (scope, elem, attr, ngModelController) => {
      const monthDayYear = 'MM-DD-YYYY';
      attr.placeholder = monthDayYear;
      
      console.log('dateDigits init');
      
      const monthDayYearParser = (viewValue) => {
        console.log('monthDayYearParser called with: ', viewValue);
        
        let parsed = moment(viewValue, monthDayYear, /*enables moment strict parsing*/ true);
        
        if (viewValue) {
          parsed = moment(viewValue, monthDayYear, /*enables moment strict parsing*/ true);
          
          if (!parsed.isValid()) {
            return undefined;
          }
        }
        
        console.log('monthDayYearParser returns ', parsed);
        return parsed;
      };
      
      const dateFormatter = (modelValue) => {
        console.log('formatter called with: ', modelValue);

        let result;
        
        if (modelValue) {
          result = modelValue.format(monthDayYear);
        }
        
        console.log('formatter returns', result);
        return result;
      };
      
      const viewChangeListener = () => {
        console.log('viewChangeListener called'); 
        console.log('viewChangeListener - $viewValue', ngModelController.$viewValue);
        console.log('viewChangeListener - $modelValue', ngModelController.$modelValue);
      }
      
      ngModelController.$validators.aValidator = (modelValue, viewValue) => {
          console.log('aValidator called', modelValue, viewValue);
          return true;
      };

      ngModelController.$viewChangeListeners.push(viewChangeListener);
      ngModelController.$parsers.push(monthDayYearParser);
      ngModelController.$formatters.push(dateFormatter);
    }
  }));