Angular: ng-class

http://angularjs.org/

HTML

<div ng-controller="MyCtrl">
  <button ng-click="useSavedPayee =!useSavedPayee">
    Click Here
  </button>
  <div class="collapse" ng-class="{'activated':!useSavedPayee}">my div</div>
  <br>
  <br>
  <div ng-class="[{'activated':!useSavedPayee}]">my div</div>
  </div>

CSS

.activated {
  border: 1px solid red;
}

JavaScript

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

function MyCtrl($scope) {

}