Get current language locale setting in the phone iOS and Android - React Native

rn-language.js

import { NativeModules, Platform } from 'react-native';

/**
 * use NativeModules to get devide languages
 * both iOS and Android, default format is language_Country e.g en_US
 * @return {string} language
 */
const deviceLanguage = Platform.OS === 'ios'
  ? NativeModules.SettingsManager.settings.AppleLocale
  : NativeModules.I18nManager.localeIdentifier;