AngularJS Example

HTML

<div ng-app="">
    <div ng-controller="Ctrl">
        <input type="text" ng-model="value">
    </div>
</div>

CSS

</style> <!-- Ugly Hack due to jsFiddle issue: http://goo.gl/BUfGZ --> 
<script src="http://docs.angularjs.org/angular-1.0.0rc8.min.js"></script>
<style>
.ng-invalid { border: 1px solid red; }

JavaScript

function Ctrl($scope) {
        $scope.$watch("value", function (scope, value) {
            $scope.$evalAsync(function () {
                console.log(value);
            });
        });
    }