[angularjs] Adding class to element using Angular JS

You can use ng-class to add conditional classes.

HTML

<button id="button1" ng-click="alpha = true" ng-class="{alpha: alpha}">Button</button>

In your controller (to make sure the class is not shown by default)

$scope.alpha = false;

Now, when you click the button, the $scope.alpha variable is updated and ng-class will add the 'alpha' class to your button.