How do I normalize CSS3 Transition functions across browsers?

Question

Webkit's transition end event is called webkitTransitionEnd, Firefox is transitionEnd, opera is oTransitionEnd. What is a good way of tackling all of them in pure JS? Should I do browser sniffing? or implement each one separately? Some other way that hasn't occurred to me?

i.e.:

//doing browser sniffing
var transitionend = (isSafari) ? "webkitTransitionEnd" : (isFirefox) ? "transitionEnd" : (isOpera) ? "oTransitionEnd";

element.addEventListener(transitionend, function(){
  //do whatever
},false);

or

// Assigning an event listener per browser
element.addEventListener("webkitTransitionEnd", fn);
element.addEventListener("oTransitionEnd", fn);
element.addEventListener("transitionEnd", fn);

function fn() {
   //do whatever
}

Answer 1

There's a technique used in Modernizr, improved:

function transitionEndEventName () {
    var i,
        undefined,
        el = document.createElement('div'),
        transitions = {
            'transition':'transitionend',
            'OTransition':'otransitionend',  // oTransitionEnd in very old Opera
            'MozTransition':'transitionend',
            'WebkitTransition':'webkitTransitionEnd'
        };

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

    //TODO: throw 'TransitionEnd event is not supported in this browser'; 
}

Then you can just call this function whenever you need the transition end event:

var transitionEnd = transitionEndEventName();
element.addEventListener(transitionEnd, theFunctionToInvoke, false);