Getting $dirty fields from angular-formly

dirty-fields.js

var dirtyFieldsIterator = function(obj, model) {
  angular.forEach(obj, function (el) {
	// fields
	if(el.fields) {
	  fieldIterator(el.fields, model);
	}
	// fieldGroup
	if(el.fieldGroup) {
	  // Nested model
	  if(el.model) { // Model $eval at runtime
		model['nested'] = {};                             // Instead of 'nested' should be `el.key`
		fieldIterator(el.fieldGroup, model['nested']);    // ""
	  } else {
		fieldIterator(el.fieldGroup, model);
	  }
	}
	// Copy regular field's value
	if(el.formControl && el.formControl.$dirty) {
	  model[el.key] = el.formControl.$modelValue || el.formControl.$viewValue;
	}
  });
};

var dirty_model = {};

dirtyFieldsIterator(vm.formFields, dirty_model);