How to use Expo with React Native

 by Robin Wieruch
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For all my React Native tutorials, I intend to use Expo as baseline, because it just makes things so much easier when developing an app with React Native. If you want to follow my tutorials about React Native, you should get this setup right.

React Native with Expo

Expo is a powerful environment for React Native which helps you from creation to distribution of your React Native apps. Without the need to directly use XCode (iOS) or Android Studio, Expo allows you to see your work in progress apps on a phone, emulator, or browser. It's fair to say that Expo makes React Native development much easier, because it takes all the friction away. When you write code in Expo, you still write React Native code, but with the support of the Expo CLI and Expo Client on your phone. We will explore both in a bit.

For the instllation of Expo, your best bet may be following the installation instructions from the official Expo documentation, because its dependencies change from time to time. However, I want to try to keep these in sync here, so you may want to follow my instructions as well.

First, you have to install Node.js. This makes npm -- the Node.js package manager -- and node itself available on the command line. Afterward, install the Expo CLI (command line interface) globally on your machine:

npm install expo-cli --global

You are ready to create your first project. Use the Expo command to initialize a new project on the command line. The name you are giving your project is up to you:

expo init myReactNativeProject

Afterward, navigate into your project and start it:

cd myReactNativeProject
expo start

After your project started, you have multiple options to develop your React Native app. The most popular one may be starting the app directly on your iOS or Android device by simply scanning the QR code after the startup with your phone's camera app. You will have to install the Expo Client from your App Store on your phone first. Other options include starting the app in your browser or on a phone emulator. Regardless of which way you choose, after starting the app make sure that it's up and running on your desired device.

Expo Configuration

Expo is a powerful suite for React Native apps, because it hides plenty of the more complex tooling for you. There are several things you can do to optimize your Expo coding experience though.

First, I like to move the entry point file -- which is by default App.js -- to another location. Therefore, create a new index.js file in your project's root folder and give it the following implementation details:

import { registerRootComponent } from 'expo';
import App from './src/App';
registerRootComponent(App);

In order to instruct Expo to take this file instead of the default App.js file in your project's root folder, open your package.json file and change the main property:

{
"main": "index.js",
"scripts": {
...
},
"dependencies": {
...
},
...
}

Last but not least, create a new src/ folder with a src/App.js file. Move your code from the old App.js file to your new src/App.js file and delete the old App.js file. Now, everything should work as before, but you have the benefit of having a dedicated source code folder for your React Native app.


If you have any other Expo configurations that you want to share with others, please write a comment below. After all, I hope you are ready to start coding with your React Native application by using Expo.

This tutorial is part 1 of 2 in this series.

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