Calculate the total time of a Youtube playlist by seconds

youtube_playlist_time.js

[...document.querySelectorAll('ytd-thumbnail-overlay-time-status-renderer>span')].map(el => {
    let timeSplit = el.innerText.split(':');
    let lastIndex = timeSplit.length - 1;
    let second = timeSplit[lastIndex] * 1;
    for (let i = 0; i < lastIndex; i++)
        second += timeSplit[i] * 60 ** (lastIndex - i);
    return second;
}).reduce((total, second) => total + second);

/* 
How to use:
1. Go to a Youtube playlist
2. Scroll to the last video of the playlist
3. F12 => Paste above code in the Console tab => Enter
4. The result is the total time of the playlist in seconds 
Note: If the miniplayer at the bottom right is in use, close that and refresh the page
*/