<!DOCTYPE html>
<html ng-app="notesApp">
<head>
    <title>Notes App</title>
    <script src="../../tp/angular.js"></script>
    <style>
        .username.ng-valid {
            background-color: greenyellow;
        }
        .username.ng-dirty.ng-invalid-required {
            background-color: hotpink;
        }
        .username.ng-dirty.ng-invalid-minlength {
            background-color: lightpink;
        }
    </style>
</head>
<body ng-controller="MainCtrl as ctrl">

<form ng-submit="ctrl.submit()" name="myForm">
    <input type="text"
           class="username"
           name="uname"
           placeholder="username"
           ng-model="ctrl.user.username"
           required
           ng-minlength="4"/>

    <input type="submit"
           value="Submit"
           ng-disabled="myForm.$invalid"/>
</form>

<script type="text/javascript">
    angular.module('notesApp', [])
        .controller('MainCtrl', [function () {
            var self = this;
            self.submit = function () {
                console.log('Submit: ', self.user);
            };
        }]);
</script>

</body>
</html>