Enables Youtube's Dark Mode using cookie

README.md

EnableYTDarkMode

This script changes Youtube's theme to dark mode by changing preferences via cookie.

Earlier, you could change YT's theme instantly by clicking the theme button.

A few weeks back, Youtube changed their site so when you click the dark mode button, it now reloads the page to change the theme instead of doing it instantly like it used to.

My browser clears cookies frequently, so I find this extra reload + waiting time very annoying

So i automated it, when youtube loads and it doesnt detect the dark mode preference value in the cookie, the script adds it and forces a reload.

Much tolerable than manually clicking the dark mode buttong and waiting for it to finish reloading ;)

EnableYTDarkMode.user.js

// ==UserScript==
// @name         Enable Youtube's Inbuilt Dark Mode (using cookies)
// @version      0.1
// @description  Enable Youtube's inbuilt Dark Mode; Useful when you frequently clear cookies
// @author       RoguedBear
// @match        https://*.youtube.com/*
// @grant        none
// @noframes
// @supportURL   https://gist.github.com/RoguedBear/56758693577fa324b1556e94d68ac6d3
// ==/UserScript==

(function () {
  "use strict";

  function setCookie(cName, cValue, expDays) {
    let date = new Date();
    date.setTime(date.getTime() + expDays * 24 * 60 * 60 * 1000);
    const expires = "expires=" + date.toUTCString();
    document.cookie =
      cName + "=" + cValue + "; " + expires + "; path=/; domain=.youtube.com";
    console.log(cName + "=" + cValue + "; " + expires + "; path=/");
  }
  // cookie to json
  // https://stackoverflow.com/a/30138647
  function cookieToJSON() {
    var cookie = document.cookie;
    var output = {};
    cookie.split(/\s*;\s*/).forEach(function (pair) {
      pair = pair.split(/\s*=\s*/);
      var name = decodeURIComponent(pair[0]);
      var value = decodeURIComponent(pair.splice(1).join("="));
      output[name] = value;
    });
    return output;
  }

  const cookies = cookieToJSON();
  if (!("PREF" in cookies) || cookies.PREF.indexOf("f6=400") === -1) {
    setCookie("PREF", "tz=UTC&f6=400", 1);
    window.location.reload();
  }
})();