Toggle DLsite Language

Switch between english and japanese language in DLsite
Ajankohdalta 6.4.2021. Katso uusin versio.
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// ==UserScript==
// @name         Toggle DLsite Language
// @namespace    zero.toogledlsitelan
// @description  Switch between english and japanese language in DLsite
// @include      *://www.dlsite.com/*
// @version      1.4
// @grant        none
// @project page https://greasyfork.org/en/scripts/402452-toggle-dlsite-language
// ==/UserScript==

(function () {
  var url = window.location.href;
  var cookies = document.cookie.split(';');
  var locale = '';

  // Get locale from cookies
  cookies.forEach(element => {
    if (element.includes('locale'))
      locale = element.substring(element.indexOf('=') + 1);
  });

  // If locale isn't found finish script and give error
  if (locale === '') {
    console.log("DLsite Toogle couldn't find locale cookie, stopping script");
    return false;
  }

  // Add toggle button
  if (url.includes('maniax')) {
    var navlink = document.getElementsByClassName('floorNavLink');
    let enButton = '<div class="floorNavLink-item type-general" style="width:125px"><a style="font-weight:bold"' +
                   'id="toggle">Toggle Site (EN)</a></div>';
    let jpButton = '<div class="floorNavLink-item type-general" style="width:125px"><a style="font-weight:bold"' +
                   'id="toggle">Toggle Site (JP)</a></div>';

    if (url.includes('?locale=')) {
      if (url.includes('ja_JP')) {
        navlink[0].innerHTML =  enButton + navlink[0].innerHTML;
      } else {
        navlink[0].innerHTML = jpButton + navlink[0].innerHTML;
      }
    } else {
      if (locale === 'ja-jp') {
        navlink[0].innerHTML = enButton + navlink[0].innerHTML;
      } else {
        navlink[0].innerHTML = jpButton + navlink[0].innerHTML;
      }
    }
  }

  // Create link on toggle button once rest of document is loaded
  document.addEventListener('DOMContentLoaded', function () {
    var toggle = document.getElementById('toggle');

    if (url.includes('?locale=')) {
      if (url.includes('ja_JP')) url = url.replace('ja_JP', 'en_US');
      else url = url.replace('en_US', 'ja_JP');
    } else {
      if (locale === 'ja-jp') url += '?locale=en_US';
      else url += '?locale=ja_JP';
    }

    toggle.href = url;
  });
})();