Get the name of the browsers transitionEnd event. After calling this, window.transitionEnd will contain the browser specific name of the transitionEnd event. This is an extract of EvandroLG's transitionEnd snippet, without all support for testing different elements and using cache.

transitionEnd.js

(function (window) {
  var transitions = {
    'transition': 'transitionend',
    'WebkitTransition': 'webkitTransitionEnd',
    'MozTransition': 'transitionend',
    'OTransition': 'otransitionend'
  },
  elem = document.createElement('div');
 
  for(var t in transitions){
    if(typeof elem.style[t] !== 'undefined'){
      window.transitionEnd = transitions[t];
      break;
    }
  }
})(window);

Thanks @Imignot!
Both valid improvements - I have updated the gist! :-)

Perhaps also consider:

if (typeof elem.style[t] !== 'undefined') {
    ....

Just in case undefined was overwrote.

Thank you @ossreleasefeed - hereby updated! :)