How to add custom validation to an AngularJS form?

Question

I have a form with input fields and validation setup by adding the required attributes and such. But for some fields I need to do some extra validation. How wou

Answer 1

Custom Validations that call a Server

Use the ngModelController $asyncValidators API which handles asynchronous validation, such as making an $http request to the backend. Functions added to the object must return a promise that must be resolved when valid or rejected when invalid. In-progress async validations are stored by key in ngModelController.$pending. For more information, see AngularJS Developer Guide - Forms (Custom Validation).

ngModel.$asyncValidators.uniqueUsername = function(modelValue, viewValue) {
  var value = modelValue || viewValue;

  // Lookup user by username
  return $http.get('/api/users/' + value).
     then(function resolved() {
       //username exists, this means validation fails
       return $q.reject('exists');
     }, function rejected() {
       //username does not exist, therefore this validation passes
       return true;
     });
};

For more information, see

• ngModelController $asyncValidators API

• AngularJS Developer Guide - Forms (Custom Validation).

---

Using the $validators API

The accepted answer uses the $parsers and $formatters pipelines to add a custom synchronous validator. AngularJS 1.3+ added a $validators API so there is no need to put validators in the $parsers and $formatters pipelines:

app.directive('blacklist', function (){ 
   return {
      require: 'ngModel',
      link: function(scope, elem, attr, ngModel) {           
          ngModel.$validators.blacklist = function(modelValue, viewValue) {
              var blacklist = attr.blacklist.split(',');
              var value = modelValue || viewValue;
              var valid = blacklist.indexOf(value) === -1;
              return valid;
          });    
      }
   };
});

For more information, see AngularJS ngModelController API Reference - $validators.

Answer 2

You can use ng-required for your validation scenario ("if these 3 fields are filled in, then this field is required":

<div ng-app>
    <input type="text" ng-model="field1" placeholder="Field1">
    <input type="text" ng-model="field2" placeholder="Field2">
    <input type="text" ng-model="field3" placeholder="Field3">
    <input type="text" ng-model="dependentField" placeholder="Custom validation"
        ng-required="field1 && field2 && field3">
</div>

Answer 3

Here's a cool way to do custom wildcard expression validations in a form (from: Advanced form validation with AngularJS and filters):

<form novalidate="">  
   <input type="text" id="name" name="name" ng-model="newPerson.name"
      ensure-expression="(persons | filter:{name: newPerson.name}:true).length !== 1">
   <!-- or in your case:-->
   <input type="text" id="fruitName" name="fruitName" ng-model="data.fruitName"
      ensure-expression="(blacklist | filter:{fruitName: data.fruitName}:true).length !== 1">
</form>

app.directive('ensureExpression', ['$http', '$parse', function($http, $parse) {
    return {
        require: 'ngModel',
        link: function(scope, ele, attrs, ngModelController) {
            scope.$watch(attrs.ngModel, function(value) {
                var booleanResult = $parse(attrs.ensureExpression)(scope);
                ngModelController.$setValidity('expression', booleanResult);
            });
        }
    };
}]);

jsFiddle demo (supports expression naming and multiple expressions)

It's similar to ui-validate, but you don't need a scope specific validation function (this works generically) and ofcourse you don't need ui.utils this way.

Answer 4

Angular-UI's project includes a ui-validate directive, which will probably help you with this. It let's you specify a function to call to do the validation.

Have a look at the demo page: http://angular-ui.github.com/, search down to the Validate heading.

From the demo page:

<input ng-model="email" ui-validate='{blacklist : notBlackListed}'>
<span ng-show='form.email.$error.blacklist'>This e-mail is black-listed!</span>

then in your controller:

function ValidateCtrl($scope) {
  $scope.blackList = ['bad@domain.com','verybad@domain.com'];
  $scope.notBlackListed = function(value) {
    return $scope.blackList.indexOf(value) === -1;
  };
}

Answer 5

In AngularJS the best place to define Custom Validation is Cutsom directive. AngularJS provide a ngMessages module.

ngMessages is a directive that is designed to show and hide messages based on the state of a key/value object that it listens on. The directive itself complements error message reporting with the ngModel $error object (which stores a key/value state of validation errors).

For custom form validation One should use ngMessages Modules with custom directive.Here i have a simple validation which will check if number length is less then 6 display an error on screen

 <form name="myform" novalidate>
                <table>
                    <tr>
                        <td><input name='test' type='text' required  ng-model='test' custom-validation></td>
                        <td ng-messages="myform.test.$error"><span ng-message="invalidshrt">Too Short</span></td>
                    </tr>
                </table>
            </form>

Here is how to create custom validation directive

angular.module('myApp',['ngMessages']);
        angular.module('myApp',['ngMessages']).directive('customValidation',function(){
            return{
            restrict:'A',
            require: 'ngModel',
            link:function (scope, element, attr, ctrl) {// 4th argument contain model information 

            function validationError(value) // you can use any function and parameter name 
                {
                 if (value.length > 6) // if model length is greater then 6 it is valide state
                 {
                 ctrl.$setValidity('invalidshrt',true);
                 }
                 else
                 {
                 ctrl.$setValidity('invalidshrt',false) //if less then 6 is invalide
                 }

                 return value; //return to display  error 
                }
                ctrl.$parsers.push(validationError); //parsers change how view values will be saved in the model
            }
            };
        });

$setValidity is inbuilt function to set model state to valid/invalid

Answer 6

I recently created a directive to allow for expression-based invalidation of angular form inputs. Any valid angular expression can be used, and it supports custom validation keys using object notation. Tested with angular v1.3.8

        .directive('invalidIf', [function () {
        return {
            require: 'ngModel',
            link: function (scope, elm, attrs, ctrl) {

                var argsObject = scope.$eval(attrs.invalidIf);

                if (!angular.isObject(argsObject)) {
                    argsObject = { invalidIf: attrs.invalidIf };
                }

                for (var validationKey in argsObject) {
                    scope.$watch(argsObject[validationKey], function (newVal) {
                        ctrl.$setValidity(validationKey, !newVal);
                    });
                }
            }
        };
    }]);

You can use it like this:

<input ng-model="foo" invalid-if="{fooIsGreaterThanBar: 'foo > bar',
                                   fooEqualsSomeFuncResult: 'foo == someFuncResult()'}/>

Or by just passing in an expression (it will be given the default validationKey of "invalidIf")

<input ng-model="foo" invalid-if="foo > bar"/>