language function does not return the expected language in nextjs middleware about negotiator HOT 3 CLOSED

Hey @kaganAhmetOkan. The Next.js team kinda shows what could be done in these docs, but not really: https://nextjs.org/docs/app/building-your-application/routing/internationalization

Like @dougwilson says, the Next.js request object isn't compatible, but you can just pass the headers to Negotiator. So you could do something like:

const locales = ['en', 'tr'];
let locale = 'en' // your default locale
const languageHeaders = request.headers.get('Accept-Language')
if (languageHeaders) {
  locale = new Negotiator({
    headers: {'accept-language': languageHeaders},
  }).language(locales)
}

Hey @jmagrippis, thank you for your help. I had not thought about passing the accept-language header directly.
.language(locales) returns undefined when there is no available language. So, I've ended up using this block of code for anyone in the future:

const locales = ["en", "tr"];
const defaultLocale = "en";
const languageHeaders = request.headers.get("Accept-Language");
const locale = new Negotiator({ headers: {"accept-language": languageHeaders }}).language(locales);

return locale ?? defaultLocale;

from negotiator.

Unfortunately it doesn't look like the request object from NextJS there is in the format this module is expecting (the type from Node.js)

from negotiator.

Hey @kaganAhmetOkan. The Next.js team kinda shows what could be done in these docs, but not really: https://nextjs.org/docs/app/building-your-application/routing/internationalization

Like @dougwilson says, the Next.js request object isn't compatible, but you can just pass the headers to Negotiator. So you could do something like:

const locales = ['en', 'tr'];
let locale = 'en' // your default locale
const languageHeaders = request.headers.get('Accept-Language')
if (languageHeaders) {
  locale = new Negotiator({
    headers: {'accept-language': languageHeaders},
  }).language(locales)
}

from negotiator.