make angular display invalid input value

make angular display invalid input value

app.directive('input', function() {
        return {
            require: '?ngModel',
            restrict: 'E',
            link: function($scope, $element, $attrs, ngModelController) {
                var inputType = angular.lowercase($attrs.type);
                
                if (!ngModelController || inputType === 'radio' ||
                        inputType === 'checkbox') {
                    return;
                }
                
                ngModelController.$formatters.unshift(function(value) {
                    if (ngModelController.$invalid && angular.isUndefined(value)
                            && typeof ngModelController.$modelValue === 'string') {
                        return ngModelController.$modelValue;
                    } else {
                        return value;
                    }
               });
           }
        };
    });