getTransitoin.js

function getTransitionEndEventName() {
  var transitions = {
      "transition"      : "transitionend",
      "OTransition"     : "oTransitionEnd",
      "MozTransition"   : "transitionend",
      "WebkitTransition": "webkitTransitionEnd"
   }
  let bodyStyle = document.body.style;
  for(let transition in transitions) {
      if(bodyStyle[transition] != undefined) {
          return transitions[transition];
      } 
  }
}