Calcula o tempo total de uma playlist no Youtube. É só colar no console na página da playlist.

ObterDuracaoPlayListYoutube.js

(function() {

var timeSeconds = 0;

var timestampList = document.querySelectorAll("div#content div#container ytd-thumbnail#thumbnail a#thumbnail div#overlays.style-scope.ytd-thumbnail.style-scope ytd-thumbnail-overlay-time-status-renderer span");

for(var i = 0; i < timestampList.length; i++) {
	
	var timestampDiv = timestampList[i];

	var timeStr = timestampDiv.innerHTML.replace("\n", "").replace("\n", "").trim();
	var timeParts = timeStr.split(":");

	var seconds = (timeParts[0] * 60) + parseInt(timeParts[1]);
	
	timeSeconds += seconds;
}

var hours = (timeSeconds / 60) / 60;
var minutes = (timeSeconds / 60) % 60;
var seconds = (timeSeconds % 60); 

var result = parseInt(hours) + ":" + parseInt(minutes) + ":" + parseInt(seconds);

var mensagem = `Tempo total Playlist: ${result}`;
    
console.log(mensagem);
alert(mensagem);
})();