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Get your development environment set up for working with React Native.


Local Setup with React Native

Now that our Hello World app is created, let's take it for a spin!

### Install the Expo Go App
You'll be testing the app on your personal mobile device. In order to do that though, you'll need to install another app called Expo Go.

The Expo Go app will sync up with the Expo command-line tools that we used to create our app in the last exercise.

- [Expo Go for Android](https://play.google.com/store/apps/details?id=host.exp.exponent) 
- [Expo Go for iOS](https://apps.apple.com/us/app/expo-client/id982107779)

### Ready, Set, Go!

Once you have the Expo Go app installed, let's run the React Native project. From inside the Visual Studio Code terminal, type the following:
- `npm start` - Starts the app

Now open up the Expo Go app you just installed, and scan the QR code which should have popped up in the terminal. 

It might take a second or two to load up, but your new React Native project should now be running on your device!

Testing the App with Expo Go

We've set up our app and tested it&mdash;now it's time to dive into the code and start doing some actual development!

### Modifying the JSX
The first thing we'll do is start playing with the JSX that's in the **App.js** file. 

Let's modify the text in the app by changing the `<Text>` component.


```jsx
<Text>Hello World</Text>
```

Once you make the change, the app should automatically update. It's just like magic! 

This process of updating the app when we save the file is called live updating, it's one of the features we get by using Expo. 

### Styles

Now let's add a little color into our app, towards the bottom of the file, modify the `styles` constant.


```js
const styles = StyleSheet.create({
  container: {
    ...
    backgroundColor: 'blue',
    ...
  }
})
```
Modifying the `backgroundColor` field will change the background color of the app to be blue. You can put any common color in place of blue and it should work!

### Debugging Errors
Inevitably, as you develop your app you'll run into errors. Luckily it's really easy to fix them when we run our app with Expo. 

Let's test this out by creating a syntax error.

Remove the `</Text>` closing tag for the Text component and save. 

```jsx
<Text>Hello World
```

This will throw an error, which should be visible on your device. With the helpful error message, it's really easy to discover exactly where the error occurred and what the problem is. 

Fix the error, save, and the app should load up again!


Modifying and Debugging the App

It's time to get Expo and React Native running on your own computer! In this lesson, we will learn how to: 
* Install the software needed to get React Native working
* Generate a basic project with the Expo command-line tools
* Preview it on your computer and, using Expo Go, preview it on your smartphone too
* Edit the application and see the changes live

Introduction

Congratulations! You've created your first Expo app. Let's take a step back and recap.

- Developing Expo apps on your own computer requires [Node.js](https://www.codecademy.com/articles/setting-up-node-locally) and a code editor.
- `npm install -g expo-cli` installs the Expo command-line tools.
- `expo init hello-world` creates a new Expo project named **hello-world**.
- Expo Go, the mobile app for [Android](https://play.google.com/store/apps/details?id=host.exp.exponent) and [iOS](https://itunes.apple.com/us/app/expo-client/id982107779), makes it easy to preview your app on your smartphone.

Review

Now that we know a bit about how Expo and React Native works, let's dive into it and create our first mobile app!

### Requirements

In order to create the app, you'll first need a few things installed on your computer:
- [Node.js](https://www.codecademy.com/articles/setting-up-node-locally) - A JavaScript runtime
- [Visual Studio Code](https://www.codecademy.com/articles/visual-studio-code) - A text editor

### Terminal Commands

Throughout the video, you'll need to enter several commands into the terminal:

- `node -v` - Checks your version of Node.js
- `npm -v` - Checks your version of Node package manager
- `npm install -g expo-cli` - Installs the Expo command-line tools
    - Expo command-line tools make it really easy to create, maintain, and test an Expo project!
- `expo init hello-world` - Creates a new Expo app
- `cd hello-world` - Moves you into the **hello-world** folder 