Get transition duration in pure JavaScript, without jQuery

getTransitionDuration.js

// Based on https://gist.github.com/snorpey/7230329

function getTransitionDuration(el){
  var res = 0
  prefix('transition-duration', function(v, pfx){
    duration = el.style[v]
    if(!duration) return
    duration = parseTime(duration) + parseTime(el.style[pfx('transition-delay')] || 0)
    function parseTime(s){ return parseFloat(s) * (s.indexOf('ms') >- 1 ? 1 : 1000) }
  })
  return res
  function prefix(str, cb, prefixes){
    prefixes = ' ' + (prefixes || 'webkit moz ms o khtml')
    prefixes.split(' ').some(function(v){
      prefix = v ? '-'+v : v
      cb(pfx(str), pfx)
      function pfx(s){ return camelCase(prefix+s) }
    })
    function camelCase(s){ return s.toLowerCase().replace(/-(.)/g, function(s, m){ return m.toUpperCase() }) }
  }
}

instead of el.style use getComputedStyle(el)

Perfect, that's exactly what I was looking for. Thank you!