Hallo,
since macOS Sierra and Safari 10 a "transitionend" is not fired for an element, which has an animation and a transition in its class definition. The behavior can be tested using this JSBIN:
http://jsbin.com/pexituteqo/edit?html,css,js,output
On previous versions of Safari and on all other modern browsers (Chrome, Firefox, IE 10) the event is fired.
A corresponding bug report has been created: 28471240.
Best,
Todor
