Puppeteer: set browser language for Chrome

browser.ts

/*
* There are multiple options to affect the user language on Chrome.
*/

const LANG = 'de';

/*
 * Set `--lang=de'` when starting Chrome
 * https://peter.sh/experiments/chromium-command-line-switches/#lang)
 */
const args = [...puppeteer.defaultArgs(), `--lang=${LANG}`];

/*
 * Set env variable `LANG` when starting Chrome
 * https://issues.chromium.org/issues/40535085#comment15
 * https://github.com/puppeteer/puppeteer/issues/5970#issuecomment-690677674
 * https://stackoverflow.com/a/71255152/1967693
 */
const env = {
  //! Note: setting this env caused Chrome to fail on certain operating systems
  LANG: LANG,
};

const browser = await puppeteer.launch({
  args,
  executablePath: puppeteer.executablePath(),
  headless: true,
  ignoreHTTPSErrors: true,
  env,
});

const page = await browser.newPage();

/*
 * Set HTTP `Accept-Language` header for page
 * https://stackoverflow.com/a/47292022/1967693
 */
await page.setExtraHTTPHeaders({
  'Accept-Language': LANG,
});

/*
 * Override `navigator.language` on the page
 * https://pptr.dev/api/puppeteer.page.evaluateonnewdocument/#example
 */
await page.evaluateOnNewDocument((lang) => {
  Object.defineProperty(navigator, 'language', {
    get() {
      return LANG;
    },
  });
  Object.defineProperty(navigator, 'languages', {
    get() {
      return [LANG];
    },
  });
}, LANG);

/* 
 * Override language with Chrome DevTools Protocol 
 * https://stackoverflow.com/questions/78481847/puppeteer-and-chrome-change-browser-language-without-restart
 * https://chromedevtools.github.io/devtools-protocol/1-3/Network/#method-setUserAgentOverride
 */
const cdpSession = await page.createCDPSession();
cdpSession.send('Network.setUserAgentOverride', {
  userAgent: await browser.userAgent(),
  acceptLanguage: LANG,
});

await page.goto(url);