index.js

if (typeof browser === 'undefined') {
  var browser = chrome;
}

const activeBtn = document.querySelector('.toggle-btn-active');
const darkBtn = document.querySelector('.toggle-btn-dark');
const debugBtn = document.querySelector('.toggle-btn-debug');
const betaBtn = document.querySelector('.toggle-btn-beta');

browser.storage.sync.get(null, function (items) {
  // Toggle button not supprted in Firefox
  if (items === undefined) {
    document.querySelector('.support-alert').innerText = `
            해당 브라우저에서는 KLAS Helper 기능을 끌 수 없습니다.
        `;
    activeBtn.checked = true;
    return;
  }
  else if (items.currentState === undefined) {
    browser.storage.sync.set({ currentState: 'ON' });
    chrome.runtime.sendMessage({
      action: 'updateIcon',
      value: 'enabled',
    });
    activeBtn.checked = true;
  }
  else if (items.currentState === 'OFF') {
    chrome.runtime.sendMessage({
      action: 'updateIcon',
      value: 'disabled',
    });
    activeBtn.checked = false;
  }
  else if (items.currentState === 'ON') {
    chrome.runtime.sendMessage({
      action: 'updateIcon',
      value: 'enabled',
    });
    activeBtn.checked = true;
  }

  // 다크테마 여부
  if (items.useDark === undefined) {
    browser.storage.sync.set({ useDark: 'OFF' });
  }
  else if (items.useDark === 'OFF') {
    darkBtn.checked = false;
  }
  else if (items.useDark === 'ON') {
    darkBtn.checked = true;
  }
});

activeBtn.onclick = function () {
  if (activeBtn.checked) {
    browser.storage.sync.set({ currentState: 'ON' });
    chrome.runtime.sendMessage({
      action: 'updateIcon',
      value: 'enabled',
    });
  }
  else {
    browser.storage.sync.set({ currentState: 'OFF' });
    chrome.runtime.sendMessage({
      action: 'updateIcon',
      value: 'disabled',
    });
  }
};

darkBtn.onclick = function () {
  if (darkBtn.checked) {
    browser.storage.sync.set({ useDark: 'ON' });
  }
  else {
    browser.storage.sync.set({ useDark: 'OFF' });
  }
};

const manifestData = browser.runtime.getManifest();
const versionElement = document.querySelector('.version');
versionElement.innerText = `v${manifestData.version}`;