Add lang hyphen, if not exists for HTML tags

Arch Linux Firefox doesn't set lang="ja" as Japanese

K instalaci tototo skriptu si budete muset nainstalovat rozšíření jako Tampermonkey, Greasemonkey nebo Violentmonkey.

You will need to install an extension such as Tampermonkey to install this script.

K instalaci tohoto skriptu si budete muset nainstalovat rozšíření jako Tampermonkey nebo Violentmonkey.

K instalaci tohoto skriptu si budete muset nainstalovat rozšíření jako Tampermonkey nebo Userscripts.

You will need to install an extension such as Tampermonkey to install this script.

K instalaci tohoto skriptu si budete muset nainstalovat manažer uživatelských skriptů.

(Už mám manažer uživatelských skriptů, nechte mě ho nainstalovat!)

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

(Už mám manažer uživatelských stylů, nechte mě ho nainstalovat!)

// ==UserScript==
// @name         Add lang hyphen, if not exists for HTML tags
// @namespace    https://github.com/patarapolw/wanikani-userscript
// @version      0.1.4
// @description  Arch Linux Firefox doesn't set lang="ja" as Japanese
// @author       polv
// @license      MIT
// @match        *://*/*
// @exclude      https://www.wanikani.com/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=eastasiastudent.net
// @grant        none
// ==/UserScript==

(() => {
  // src/fix-lang-hyphen.ts
  var FIX_LANG_HYPHEN = {
    ja: "",
    ko: "",
    zh: "",
    vi: ""
  };
  getLang(document.documentElement);
  fixLangObserver();
  function fixLangObserver(el = document.body) {
    new MutationObserver((muts) => {
      for (const mut of muts) {
        mut.addedNodes.forEach((n) => {
          if (n instanceof HTMLElement) {
            findAndFixLang(n);
          }
        });
      }
    }).observe(el, {
      childList: true,
      subtree: true
    });
    findAndFixLang(el);
  }
  function findAndFixLang(el) {
    el.querySelectorAll("*").forEach((it) => getLang(it));
  }
  function getLang(it, fix = true) {
    let aLang = it.getAttribute("lang");
    if (aLang && typeof FIX_LANG_HYPHEN[aLang] === "string") {
      aLang += "-" + FIX_LANG_HYPHEN[aLang];
      if (fix) {
        it.setAttribute("lang", aLang);
      }
      return aLang;
    }
    return null;
  }
})();