animations.js

  var animationHelpers = {

    determineTransition: function() {
      // technique from:
      // https://github.com/dmotz/oriDomi/blob/master/oridomi.js#L80
      // @TODO cache value so it doesn't keep getting looked up
      var prefixList, testEl, supportedProp;

      prefixList = ['webkit', 'Moz', 'O', 'ms', 'Khtml'];
      testEl = document.createElement('div');

      supportedProp = testEl.style['transitionProperty'] != null ?
        'transitionProperty' :
        _.find(prefixList, function(prefix) {
          return testEl.style[prefix + 'TransitionProperty'] != null;
        }) + 'TransitionProperty';

      // deal with crossover issues between webkit & moz
      if(supportedProp == 'transitionProperty'
         && testEl.style['webkitTransitionProperty'] != null) {
        supportedProp = 'webkitNew';
      }

      switch (supportedProp) {
        case 'webkitNew':
          return 'webkitTransitionEnd';
        case 'transitionProperty':
          return 'transitionend';
        case 'webkitTransitionProperty':
          return 'webkitTransitionEnd';
        case 'MozTransitionProperty':
          return 'transitionend';
        case 'OTransitionProperty':
          return 'oTransitionEnd';
        case 'MSTransitionProperty':
          return 'msTransitionEnd';
      }
    },

    onTransitionEnd: function(el, fn) {
      var transition = this.determineTransition();
      el.addEventListener(transition, fn, false);
    },

    offTransitionEnd: function(el, fn) {
      var transition = this.determineTransition();
      el.removeEventListener(transition, fn, false);
    }

  };