Egghead total duration of a course..

egghead-total-duration.js

(function (s) {
  return [~~(s / 3600), ~~((s % 3600) / 60), s % 60].map(v => v < 10 ? '0' + v : v).join(':');
})([].slice.call(document.querySelectorAll('.duration'))
.filter((e, i, a) => ++i <= (a.length / 3))
.map(h => {
  var t = h.textContent.match(/[0-9]{1,2}:[0-9]{1,2}/);
  var p = t[0].split(':').map(Number);
  return (p[0] * 60) + p[1]
}).reduce((p, c) => p + c, 0));