Extracting the transition with the longest duration (and delay)

durationtransitionprop.js

function getMaxDurationTransitionProperty(el) {
    // small helper to extract the values
    function extract(str) {
        return str
          .replace(/[A-Z]/gi, "")
          .split(", ")
          .map(parseFloat);
    };
  // get the current style
  var style = getComputedStyle(el);
  // get all transition properties
  var props = style.transitionProperty.split(", ");
  // we need delay and duration
  var delays = extract(style.transitionDelay);
  var durations = extract(style.transitionDuration);

  // combinate delay and duration
  var totals = durations.map(function(v, i) {
    return v + delays[i];
  });

  // find the property with longest value
  var max = totals[0]; 
  var maxIndex = 0;
  for (var i = 1; i < totals.length; i++) {
    if (totals[i] > max) {
      maxIndex = i;
      max = totals[i];
    }
  }
  // and return this property
  return props[maxIndex];
}