Let me just add that checking for the presence of
TransitionEvent looks to be a perfectly lean feature test for
transition capability in general. Although for the specifics on the prefix of the event listener one would still have to access some element style (not by necessarily creating a new element though), if you want to decide in a script whether to use CSS transition by adding a class or creating the animation with jQuery for example this test could very well serve it’s purpose.
I’m still wondering if it’ll return
true with some of the older browsers that were using the now deprecated constructor…