Youtube classic playlist auto next toggle

youtubeClassicPlaylistAutoNextToggle.user.js

// ==UserScript==
// @name        Playlist auto next toggle - youtube.com
// @namespace   Violentmonkey Scripts
// @match       https://www.youtube.com/watch
// @grant       none
// @version     1.0
// @author      -
// @description 4/24/2020, 10:01:32 AM
// ==/UserScript==

/*
For Firefox user who uses youtube classic. 
A checkbox would be added to control whether to auto play next in playlist
*/

let control = document.querySelector('.playlist-nav-controls');

if(!control) {
  return;
}

let k = Object.keys(window._yt_www)
	.filter(key => typeof window._yt_www[key] === "function")
	.find(key => String(window._yt_www[key]).split("spf.navigate").length > 1);

if(!k) {
  return;
}

let ori = window._yt_www[k];

window._yt_www[k] = function() { 
    if(localStorage.getItem('playlistAutoplay') === 'true'){ 
        ori.apply(this, arguments); 
    }
}


var cb = document.createElement('input');
cb.setAttribute('type', 'checkbox');
cb.style.verticalAlign = 'middle';
cb.checked = localStorage.getItem('playlistAutoplay') === 'true';
cb.addEventListener('change', function(){
    localStorage.setItem('playlistAutoplay', cb.checked? 'true':'false');
});
var label = document.createElement('label');
label.appendChild(cb);
label.appendChild(document.createTextNode('auto next'));
label.style.paddingLeft = '8px';
control.appendChild(label);