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function whichTransitionEvent(){
    var t;
    var el = document.createElement('fakeelement');
    var transitions = {
      'transition':'transitionend',
      'MSTransition':'msTransitionEnd',
      'MozTransition':'transitionend',
      'WebkitTransition':'webkitTransitionEnd'
    }

    for(t in transitions){
        if( el.style[t] !== undefined ){
            return transitions[t];
        }
    }
}