Get playtime of a youtube playlist

get_playtime.js

var list = document.getElementsByClassName('ytd-thumbnail-overlay-time-status-renderer');
var time = 0;

function toS(hms) {
  var a = hms.split(':');
  while (a.length < 3) {
    a.unshift(0);
  }
  var seconds = (+a[0]) * 60 * 60 + (+a[1]) * 60 + (+a[2]);
  return seconds;
}

function toHMS(totalSec) {
  var hours = parseInt( totalSec / 3600 );
  var minutes = parseInt( totalSec / 60 ) % 60;
  var seconds = totalSec % 60;
  var result = (hours < 10 ? "0" + hours : hours) + ":" + (minutes < 10 ? "0" + minutes : minutes) + ":" + (seconds  < 10 ? "0" + seconds : seconds);
  return result;
}

function add(item) {
   /*item = item.getElementsByClassName('timestamp')[0];
   item = item.getElementsByTagName('SPAN')[0]; */
   var timeString = (item.innerText || item.textContent);
   time += toS(timeString);
}

for (var i = 0; i < list.length; i++) {
  var item = list[i];
  add(item);
}

console.log("The full duration time is: " + toHMS(time));

One Liner to paste into Browser Console:

var list=document.getElementsByClassName("ytd-thumbnail-overlay-time-status-renderer"),time=0;function toS(t){for(var e=t.split(":");e.length<3;)e.unshift(0);return 60*+e[0]*60+60*+e[1]+ +e[2]}function toHMS(t){var e=parseInt(t/3600),i=parseInt(t/60)%60,n=t%60;return(e<10?"0"+e:e)+":"+(i<10?"0"+i:i)+":"+(n<10?"0"+n:n)}function add(t){var e=t.innerText||t.textContent;time+=toS(e)}for(var i=0;i<list.length;i++){var item=list[i];add(item)}console.log("The full duration time is: "+toHMS(time));