Hey Alex, thanks for your effort.
In Safari, I get the error - TypeError: undefined is not an object (near '...null).click();...')
In Chrome, It just keeps printing - youtube_player_api_elements NodeList 
I tried it in youtube.com as suggested, shouldn't it be done in https://www.youtube.com/feed/channels ? I had to close the browser each time to quit this, I understand that this is a test but a more intuitive browser extension based solution would be much appreciated.