detectLanguage

Detects the preferred language of the current user.

• Use NavigationLanguage.language or the first NavigationLanguage.languages if available, otherwise return defaultLang.
• Omit the second argument, defaultLang, to use 'en-US' as the default language code.

const detectLanguage = (defaultLang = 'en-US') => 
  navigator.language ||
  (Array.isArray(navigator.languages) && navigator.languages[0]) ||
  defaultLang;

detectLanguage(); // 'nl-NL'