How to use a standalone Expo module

Learn how to use a standalone module created with create-expo-module in your project by using a monorepo or publishing the package to npm.

The recommended way to create an Expo module inside an existing application is described in the Expo Modules API: Get started guide. This page outlines two additional methods of using a module created with create-expo-module inside an existing project:

• Configure a monorepo
• Publish the module to npm

These methods are useful if you still want to keep the module separate from the application or share it with other developers.

Use a monorepo

For this guide, we assume that you have the following project structure:

• apps/ - Contains multiple projects, including React Native apps.
• packages/ - Contains different packages used by your apps.
• package.json - Root package file containing Yarn workspaces config.

If you need to familiarize yourself with configuring your project as a monorepo, see Working with monorepos guide.

1. Initialize a new module

Once you have set up the basic monorepo structure, create a new module using create-expo-module with the flag no-example to skip creating the example app:

2. Set up workspace

Now, let's configure autolinking so all your apps can use the newly created module. Add the following block to the package.json file of each app under the apps directory:

"expo": {
  "autolinking": {
    "nativeModulesDir": "../../packages"
  }
}

3. Run the module

Run one of the apps to ensure everything is working. Then, start the TypeScript compiler inside packages/expo-settings to watch for changes and rebuild the module's JavaScript:

Open another terminal window, choose an app from the apps directory, and run the prebuild command. You'll have to repeat these steps for all apps inside your monorepo to use the new module.

Compile and run the app with the following command:

You can now use the module inside your app. To test this, let's edit the App.js file in the app and render the text message from the expo-settings module:

import * as Settings from 'expo-settings';
import { StatusBar } from 'expo-status-bar';
import React from 'react';
import { Text, View } from 'react-native';

export default function App() {
  return (
    <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
      <Text>{Settings.hello()}</Text>
      <StatusBar style="auto" />
    </View>
  );
}

After this configuration, you'll see a text that says "Hello world! 👋" in the app.

Publish the module to npm

You can publish the module on npm and then add it to your project by installing it as a dependency.

1. Initialize a new module

Start by creating a new module using create-expo-module. Pay attention to each prompt as you'll publish this library, and choose a unique name for your npm package.

2. Run the example project

Run the example project to make sure everything is working. Then, start the TypeScript compiler to watch for changes and rebuild the JavaScript module.

Open another terminal window, compile and run the example app:

3. Publish the package to npm

To publish your package to npm, you need to have a npm account. If you don't have one, create it on the npm website. Once you have an account, log in using the following command:

Then, navigate to the root of your module and publish your module running:

Your module will now be published to npm and can be installed in other projects using npm install.

Apart from publishing your module to npm, there are other ways to use it in your project:

• Create a tarball of your module using npm pack and install it directly in your project by running npm install /path/to/tarball. It's useful to test your module locally before publishing it to npm or if you want to share it with others who don't have access to the npm registry.
• Run a local npm registry, such as Verdaccio, and install your module from there. This is useful for cases where you want to host your private npm registry to manage internal packages within a company or organization.
• Publish a private package or use a private registry with EAS Builds.

4. Test the published module

To test the published module in a new project, create a new app and install the module as a dependency:

You should now be able to use the module inside your app! To test it, edit the App.js in the app and render the text message from expo-settings.

import * as Settings from 'expo-settings';
import { StatusBar } from 'expo-status-bar';
import React from 'react';
import { Text, View } from 'react-native';

export default function App() {
  return (
    <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
      <Text>{Settings.hello()}</Text>
      <StatusBar style="auto" />
    </View>
  );
}

To run your app locally, run the prebuild command and then compile the app.

After this configuration, you'll see a text that says "Hello world! 👋" in the app.