Awesome

ReactNativeLocalization

Class to localize the ReactNative interface.

Use react-localization if you want to share code with a React project or the localized-strings for a generic javascript solution.

Note about version 1.x

This library has been refactored to use the newly created localized-strings package, now added as a dependency, so to unify the code and make it easier to mantain

All the basic code is now in the localized-strings project and in the react-localization version that adds support for embedding JSX code in the formatted strings, by overriding the formatString method.

This version adds a custom version of the getInterfaceLanguage to retrieve the interface language from the native OS.

To simplify Android versions' configuration, versions 2.0 and up are compatible only with ReactNative >= 0.56.0

What it does

I just needed a dead simple way to internationalize my first React Native app.

At the beginning I thought I'd expose the native iOS internationalization API (NSLocalizedString macro) to React Native, but then I've opted for a solution that seems, at least to me, more in the spirit of React (and I hope better performance wise).

In this implementation we can keep the localized strings in the same file of the React View in a similar way of how Styles are implemented (I don't deny that this approach could lead to some duplications in the translated strings, but it could be feasible to create a CommonJS module to use as common source of the strings, requiring it in the different views).

Beware Expo created apps need to be ejected before integrating native plugins like this one. So if you've used the Create React Native app shortcut you should eject the app as detailed here here.

How it works

The Javascript library uses a native library (ReactLocalization) to get the current interface language, then it loads and displays the strings matching the current interface locale or the default language (the first one if a match is not found) if a specific localization can't be found.

It's possible to force a language different from the interface one.

Installation

The easiest way to install is to type just 2 commands inside your react-native project folder and you are ready to go:

yarn add react-native-localization 

or

npm i react-native-localization

#react-native >= 0.60
cd ios && pod install && cd ..

#react-native < 0.60
react-native link react-native-localization

Don´t forget to restart the app / node server or you will see an error.

If you're installing for Android and still experiencing problems check if step 4 of "Manual installation Android" has been automatically executed by the linker.

Check this article about the new linking behaviour in react-native since version 0.60.

Windows platform doesn't support automatic installation by linker. Only manual installation is supported.

Manual installation iOS

npm install --save react-native-localization
In the XCode's "Project navigator", right click on Libraries folder under your project ➜ Add Files to <...>
Go to node_modules ➜ react-native-localization and add the ReactNativeLocalization.xcodeproj file
Add libReactNativeLocalization.a to Build Phases -> Link Binary With Libraries
Build and run

Manual installation Android

npm install --save react-native-localization

In android/setting.gradle

...
include ':react-native-localization', ':app'
project(':react-native-localization').projectDir = new File(rootProject.projectDir, '../node_modules/react-native-localization/android')

In android/app/build.gradle

...
dependencies {
    ...
    compile project(':react-native-localization')
}

import com.babisoft.ReactNativeLocalization.ReactNativeLocalizationPackage; // <--- import

public class MainApplication extends Application implements ReactApplication {
  ......
    @Override
    protected List<ReactPackage> getPackages() {
      return Arrays.<ReactPackage>asList(
          new MainReactPackage(),
          new ReactNativeLocalizationPackage()
      );
    }
  ......
}

(Thanks to @rebeccahughes for showing by example how to create an android module for React Native)

Manual installation windows

Full process is documented in official React Native plugin for Universal Windows repo: https://github.com/Microsoft/react-native-windows/blob/master/docs/LinkingLibrariesWindows.md

Run npm install --save react-native-localization
Open your Visual Studio solution.
Right-click the solution in the Solution Explorer
Select Add -> Existing Project
Choose the .csproj of the dependency from the Explorer window. Dependency will be in node_modules\react-native-localization\windows\ReactNativeLocalization
Right-click the Universal Windows App project in the Solution Explorer
Select Add -> Reference
Choose the ReactNativeLocalization project.
Open MainPage.cs
Add the new ReactNativeLocalization.RNLocalizationPackage() to the Packages list in MainPage.cs

Usage

In the React class that you want to localize require the library and define the strings object passing to the constructor a simple object containing a language key (i.e. en, it, fr..) and then a list of key-value pairs with the needed localized strings.

// ES6 module syntax
import LocalizedStrings from 'react-native-localization';

// CommonJS syntax
// let LocalizedStrings  = require ('react-native-localization');

let strings = new LocalizedStrings({
 "en-US":{
   how:"How do you want your egg today?",
   boiledEgg:"Boiled egg",
   softBoiledEgg:"Soft-boiled egg",
   choice:"How to choose the egg"
 },
 en:{
   how:"How do you want your egg today?",
   boiledEgg:"Boiled egg",
   softBoiledEgg:"Soft-boiled egg",
   choice:"How to choose the egg"
 },
 it: {
   how:"Come vuoi il tuo uovo oggi?",
   boiledEgg:"Uovo sodo",
   softBoiledEgg:"Uovo alla coque",
   choice:"Come scegliere l'uovo"
 }
});

Then use the strings object literal directly in the render method accessing the key of the localized string.

<Text style={styles.title}>
  {strings.how}
</Text>

The first language is considered the default one, so if a translation is missing for the selected language, the default one is shown and a line is written to the log as a reminder.

Update / Overwrite Locale

You might have default localized in the build but then download the latest localization strings from a server. Use setContent to overwrite the whole object. NOTE that this will remove all other localizations if used.

strings.setContent({
  en:{
    how:"How do you want your egg todajsie?",
    boiledEgg:"Boiled eggsie",
    softBoiledEgg:"Soft-boiled egg",
    choice:"How to choose the egg"
  }
})

You can also only overwrite a specific language using

strings.setContent(Object.assign({},strings.getContent(),
{
  en:{
    how:"How do you want your egg todajsie?",
    boiledEgg:"Boiled eggsie",
    softBoiledEgg:"Soft-boiled egg",
    choice:"How to choose the egg"
  }
}));

Typescript

For TypeScript, your tsconfig.json should be something like this:

{
    "compilerOptions": {
        "target": "es2015",
        "module": "es2015",
        "jsx": "react-native",
        "moduleResolution": "node",
        "allowSyntheticDefaultImports": true
    }
}

Where "module": "es2015" is the most important setting for being able to import the module properly.

Import should be done like this:

import LocalizedString from "react-native-localization";

API

setLanguage(languageCode) - to force manually a particular language
getLanguage() - to get the current displayed language
getInterfaceLanguage() - to get the current device interface language
formatString() - to format the passed string replacing its placeholders with the other arguments strings

  en:{
    bread:"bread",
    butter:"butter",
    question:"I'd like {0} and {1}, or just {0}"
  }
  ...
  strings.formatString(strings.question, strings.bread, strings.butter)

Beware: do not define a string key as formatString or language!

getAvailableLanguages() - to get an array of the languages passed in the constructor

Examples

To force a particular language use something like this:

_onSetLanguageToItalian() {
  strings.setLanguage('it');
  this.setState({});
}

It's also possible to set the language directly in your Xcode project using the following code snippet:

[[NSUserDefaults standardUserDefaults] setObject:[NSArray arrayWithObjects:@"de", nil] forKey:@"AppleLanguages"];

Replace de with a supported locale identifier to test.

Check out the WIKI page for additional informations.

Questions or suggestions?

Feel free to contact me on Twitter or open an issue.