Something similar to [NSLocale currentLocale] in Objective-C.
There's no need for an external library. You can find what you're looking for in React's Native Modules
import { NativeModules } from 'react-native'
// iOS:
const locale = NativeModules.SettingsManager.settings.AppleLocale ||
NativeModules.SettingsManager.settings.AppleLanguages[0] // "fr_FR"
// Android:
const locale = NativeModules.I18nManager.localeIdentifier // "fr_FR"
To test this, I changed the language on my device to French. Here's a sample of what you'll find in the NativeModules.SettingsManager.settings object related to locale:
{
...
AppleKeyboards: [
"fr_FR@hw=US;sw=QWERTY",
"en_US@sw=QWERTY;hw=Automatic",
"es_419@sw=QWERTY-Spanish;hw=Automatic",
"emoji@sw=Emoji"
]
AppleLanguages: ["fr-US", "en-US", "es-US", "en"]
AppleLanguagesDidMigrate: "9.2"
AppleLocale: "fr_FR"
NSLanguages: ["fr-US", "en-US", "es-US", "en"]
...
}