title: detect if element is being transitioned
body: <p>How to detect via js if any sort of transition is being applied to the element right now?</p>
  <h3>Short story of my problem:</h3>
  I have a situation where I'm firing a function on the `transitionend` event, but sometimes the element doesn't have any *transition* being applied (because in Firefox, for example, the user might click some element rapidly which makes the transition goes crazy and stop working) so I want to know when it doesn't work and just fire the function myself, skipping the `transitionend`. I am trying to avoid ugly solutions..