JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app>
    <div ng-controller="test">
        <div ng-class="classToBeUsed">
            TEST
        </div>
        <div ng-class="abc: !setThisClass">
            CLASS NOT APPLIED
        </div>
    </div>
</div>

CSS

.abc{
    font-size:larger;
    font-weight:bold;
}

JavaScript

function test($scope){
    $scope.classToBeUsed = 'abc';
    $scope.setThisClass = true;
}