javascript - AngularJs form validation doesn't work -

i new on angular js, working on form validations. have done still validation doesn't work. here code:

<form role="form" name="studentform" class="form-horizontal" novalidate>     <div class="form-group">         <label for="student_email" class="col-sm-2 control-label">email</label>         <div class="col-sm-10">             <input type="email" name="student_email" ng-model="studentemail" class="form-control" id="student_email" required>             <div role="alert" class="error-msg" ng-messages="studentform.student_email.$error">                 <p ng-message="required">your email required.</p>             </div>         </div>     </div> </form> 

script:

angular.module('app', ['ngmessages']); 

here working demo code.

 <script src="//ajax.googleapis.com/ajax/libs/angularjs/1.5.5/angular.min.js"></script>  <script src="//ajax.googleapis.com/ajax/libs/angularjs/1.5.5/angular-messages.js"></script>  <script src="script.js"></script> 

may forgot add scripts in html files. position of scripts in index.html file matters. ng-message should include below angular.min.js

please check demo