[SOLVED] How can I get the name of a language in any other language, based on IETF language tag

How can I get the name of a language in any other language, based on IETF language tag

I'm looking for a way to get the name of a language in any other language, based on a IETF language tag. For example: I have a list of IETF language tags ('en', 'fr', 'nl', 'de' , ...) and I want them mapped to the language display name of my current locale (e.g. Dutch):

'en' => 'Engels'
'fr' => 'Frans'
'nl' => 'Nederlands'
'de' => 'Duits'

I've searched NPM but found nothing. I would prefer a list in JSON, but I will settle for any language/format.

EDIT: Solution

This is how you can implement this using cldr-localenames-modern (see @korpiq's answer below):

import en from 'cldr-localenames-modern/main/en/languages.json';
import nl from 'cldr-localenames-modern/main/nl/languages.json';

const localeDisplayNames = {
    en: en.main.en.localeDisplayNames.languages,
    nl: nl.main.nl.localeDisplayNames.languages
};

export function getLanguageDisplayName(language, locale) {
    const languages = localeDisplayNames[locale] ?? localeDisplayNames['en'];

    return languages[language];
}

Solution

This is the closest I have found so far: https://github.com/unicode-org/cldr-json/tree/main/cldr-json/cldr-localenames-modern

However, there the displayNames in each locale's languages.json are tagged by 2-3 letter codes, instead of the <language>-<country> naming used for the locales themselves. For two-letter names, I guess it's sufficient.