angularjs form validation

Official documentation is pretty good.

novalidate is used to disable browser’s native form validation.

A form is an instance of FormController. The form instance can optionally be published into the scope using the name attribute.

Similarly, an input control that has the ngModel directive holds an instance of NgModelController. Such a control instance can be published as a property of the form instance using the name attribute on the input control. The name attribute specifies the name of the property on the form instance.

This implies that the internal state of both the form and the control is available for binding in the view using the standard binding primitives.

This allows us to extend the above example with these features:

  • Custom error message displayed after the user interacted with a control (i.e. when $touched is set)
  • Custom error message displayed upon submitting the form ($submitted is set), even if the user didn’t interact with a control

By default, any change to the content will trigger a model update and form validation. You can override this behavior using thengModelOptions directive to bind only to specified list of events. I.e. ng-model-options="{ updateOn: 'blur' }" will update and validate only after the control loses focus. You can set several events using a space delimited list."{ updateOn: 'mousedown blur' }"

Custom validation could be added thru directive by calling ngModel.$validators.customField = function(modelValue, viewValue){// true or false logic}

Async custom validation uses $asyncValidators and should return a promise.

To modify the built in validation, just overwrite the corresponding field in $validators in link function:

ctrl.$ = function(modelValue) {
          return ctrl.$isEmpty(modelValue) || EMAIL_REGEXP.test(modelValue);

require: ‘ngModel’

Note many of the link function has

require: 'ngModel',

It means :

The require instruction gives you the controller for the directive you name as the fourth argument to your link function. (You can use ^ to look for the controller on a parent element; ? makes it optional.) So require: 'ngModel' gives you the controller for the ngModel directive, which is an ngModelController.

Directive controllers can be written to provide APIs that other directives can use; with ngModelController, you get access to special functionality that’s built into ngModel, including getting and setting the value. Consider the following example:

<input color-picker ng-model="project.color">
app.directive('colorPicker', function() {
  return {
    require: 'ngModel',
    link: function(scope, element, attrs, ngModel) {
        // initialize the color to the color on the scope
        pickerDefault: scope.color,
        // update the ngModel whenever we pick a new color
        onColorChange: function(id, newValue) {
          scope.$apply(function() {

      // update the color picker whenever the value on the scope changes
      ngModel.$render = function() {

This directive uses the ngModel controller to get and set the value of the color from the colorpicker. See this JSFiddle example:

If you’re using require: 'ngModel', you probably shouldn’t also be using ngModel: '=' in your isolate scope; the ngModelController gives you all the access you need to change the value.

The bottom example on the AngularJS homepage also uses this functionality (except using a custom controller, not ngModel).


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