Angular: Empty Fiddle

http://angularjs.org/

HTML

<script src="http://code.angularjs.org/angular-1.0.1.js"></script>
<form name="login" class="form-horizontal" ng-controller="LoginFormCtrl">
  <div class="control-group"
     ng-class="{error: login.username.$error.required && !login.$pristine}">
    <label class="control-label" for="{{input.name}}">Username </label>

    <div class="controls">
        <input type="text" id="{{input.name}}"
               placeholder="{{input.placeholder}}"
               name="{{input.name}}" ng-model="username" required/>
                <span class="help-inline"
                      ng-show="login.{{input.name}}.$error.required && !login.$pristine">Required!</span><br>
    </div>
</div>
</form>

JavaScript

var myApp = angular.module('myApp',[]);

//myApp.directive('myDirective', function() {});
//myApp.factory('myService', function() {});

function LoginFormCtrl($scope) {
    $scope.input = {name: 'username',placeholder: 'Username',label: 'Username'};
}