transition_sniffing.js

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];
        }
    }
}

The way you get around firing function twice is to add a namespace to the event name and turning them all off once one of them have been executed.

this.$el.on('webkitTransitionEnd.blah transitionend.blah msTransitionEnd.blah oTransitionEnd.blah', function(event) {
  this.$el.off(".blah");
}

Obviously, replace blah with your own namespace.