Is there a way to check if there is a class named 'some-class-name' in css?

For example, I have:

<style type="text/css">
    .box {
        position: absolute;
        left: 150%;
    }
</style>

My intention is to randomly assign a class to a div on certain event:

var classList = []; //Need to populate this array
$('#updateClass').on('click', function() {
    $('#resultDiv').attr('class',classList[Math.floor((Math.random()*classList.length)+1)]);
}); 

Is it possible to check by JS/jQuery whether a class named 'box' exists in the stylesheet?

Thanks.