How to fire an event on class change using jQuery?

There is no event raised when a class changes. The alternative is to manually raise an event when you programatically change the class:

$someElement.on('event', function() {
    $('#myDiv').addClass('submission-ok').trigger('classChange');
});

// in another js file, far, far away
$('#myDiv').on('classChange', function() {
     // do stuff
});

---

UPDATE

This question seems to be gathering some visitors, so here is an update with an approach which can be used without having to modify existing code using the new MutationObserver:

var $div = $("#foo");
var observer = new MutationObserver(function(mutations) {
  mutations.forEach(function(mutation) {
    var attributeValue = $(mutation.target).prop(mutation.attributeName);
    console.log("Class attribute changed to:", attributeValue);
  });
});

observer.observe($div[0], {
  attributes: true,
  attributeFilter: ['class']
});

$div.addClass('red');

.red {
  color: #C00;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="foo" class="bar">#foo.bar</div>

Expand snippet

Be aware that the MutationObserver is only available for newer browsers, specifically Chrome 26, FF 14, IE 11, Opera 15 and Safari 6. See MDN for more details. If you need to support legacy browsers then you will need to use the method I outlined in my first example.