JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
<div ng-app>
    <div ng-controller="test">
        <button class="btn btn-link" ng-click="buttonClicked()"><span ng-class="{'glyphicon-chevron-down':!clicked,'glyphicon-chevron-right':clicked,'glyphicon':true}"></span>
        </button>
    </div>
</div>

JavaScript

function test($scope) {
    $scope.clicked = false;
    $scope.buttonClicked = function(){
        $scope.clicked = !$scope.clicked;
    }
}