code: function _whichTransitionEvent() {
      const el = document.createElement('meta');
      const animations = {
          transition: 'transitionend',
          OTransition: 'oTransitionEnd',
          MozTransition: 'transitionend',
          WebkitTransition: 'webkitTransitionEnd',
      };
  
      for (const t in animations) {
          if (el.style[t] !== undefined) {
              return animations[t];
          }
      }
  }
docs: Detect what transition property to listen for
  
  @returns {*}
  @private