Expo Go for quick start in React Native - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Expo Go in React Native development?

Expo Go is a mobile app that lets you run React Native projects instantly on your phone without building native code. It helps you see your app live while coding.

beginner

How does Expo Go simplify starting a React Native app?

Expo Go removes the need to install Android Studio or Xcode first. You just scan a QR code from your development computer and your app runs on your phone immediately.

beginner

Which command starts a new Expo project that works with Expo Go?

You use npx create-expo-app myApp to create a new project ready to run in Expo Go.

intermediate

Can you use Expo Go to test native device features like camera or GPS?

Yes, Expo Go supports many native device features through Expo APIs, so you can test camera, GPS, sensors, and more without extra setup.

intermediate

What is a limitation of using Expo Go for app development?

Expo Go cannot run custom native code or third-party native modules that are not included in Expo. For those, you need to build a custom development client or eject.

What do you need to do to run your React Native app on your phone using Expo Go?

A Build a native APK or IPA file first

B Scan a QR code from the Expo development server

C Install Android Studio on your phone

D Write native Java or Swift code

Expo Go lets you run your app by scanning a QR code from the development server, no need to build native files first.

Which command creates a new Expo project ready for Expo Go?

A npx create-expo-app myApp

B npx create-react-app myApp

C expo init myApp

D react-native init myApp

The command npx create-expo-app myApp creates a new Expo project compatible with Expo Go.

What is a key benefit of using Expo Go for beginners?

A No need to install native SDKs like Xcode or Android Studio

B You can write native Java and Swift code directly

C It automatically publishes your app to app stores

D It replaces the need for React Native

Expo Go removes the need to install native SDKs, making it easier for beginners to start coding quickly.

Which of these is NOT supported directly by Expo Go?

A Live reloading your app during development

B Accessing GPS location

C Using device camera

D Running custom native modules not included in Expo

Expo Go cannot run custom native modules that are not part of the Expo SDK.

How does Expo Go help with app testing?

A It automatically fixes code errors

B It compiles your app into a final store-ready package

C It lets you see changes instantly on your phone as you code

D It replaces the need for physical devices

Expo Go supports live reloading so you can see your app update instantly on your phone.

Explain how Expo Go makes starting React Native development easier for beginners.

Think about what setup steps Expo Go removes.

Describe a limitation of Expo Go and how developers can work around it.

Consider what happens if you need native code not in Expo.

Practice

1. What is the main purpose of Expo Go in React Native development?

easy

A. To run React Native apps instantly on your phone without complex setup

B. To compile native code for Android and iOS manually

C. To replace the need for JavaScript in app development

D. To create backend APIs for mobile apps

Solution

1. Step 1: Understand Expo Go's role

   Expo Go allows developers to run React Native apps quickly on their phones without building native code.

2. Step 2: Compare options

   Compiling native code manually, replacing the need for JavaScript, and creating backend APIs are unrelated tasks. Only running React Native apps instantly on your phone without complex setup matches Expo Go's purpose.

3. Final Answer:

   To run React Native apps instantly on your phone without complex setup -> Option A

4. Quick Check:

   Expo Go = Quick app running [OK]

Hint: Expo Go runs apps instantly on devices without building [OK]

Common Mistakes:

• Thinking Expo Go compiles native code manually
• Confusing Expo Go with backend tools
• Assuming Expo Go replaces JavaScript

2. Which command starts a new Expo project using Expo CLI?

easy

A. react-native init MyApp

B. expo start new MyApp

C. npm run expo create MyApp

D. expo init MyApp

Solution

1. Step 1: Recall Expo CLI commands

   The correct command to create a new Expo project is expo init MyApp.

2. Step 2: Eliminate incorrect commands

   'expo start new MyApp' is invalid syntax, 'npm run expo create MyApp' mixes npm and expo incorrectly, 'react-native init MyApp' is for React Native CLI, not Expo.

3. Final Answer:

   expo init MyApp -> Option D

4. Quick Check:

   New Expo project = expo init [OK]

Hint: Use 'expo init' to start new projects [OK]

Common Mistakes:

• Using 'expo start' to create projects
• Confusing React Native CLI with Expo CLI
• Trying npm commands for Expo project creation

3. What will happen when you run expo start in your project folder?

medium

A. It opens a QR code in the terminal to scan with Expo Go app

B. It builds a native APK file automatically

C. It deploys the app to the App Store

D. It deletes the project files

Solution

1. Step 1: Understand 'expo start' command

   This command starts a development server and shows a QR code to open the app in Expo Go.

2. Step 2: Check other options

   Deploying the app to the App Store, building a native APK file automatically, and deleting the project files are not what 'expo start' does.

3. Final Answer:

   It opens a QR code in the terminal to scan with Expo Go app -> Option A

4. Quick Check:

   expo start = QR code for Expo Go [OK]

Hint: expo start shows QR code to open app in Expo Go [OK]

Common Mistakes:

• Expecting 'expo start' to build app files
• Confusing deployment with development commands
• Thinking 'expo start' deletes files

4. You ran expo start but the QR code does not appear. What is a likely fix?

medium

A. Delete the node_modules folder

B. Run npm uninstall expo

C. Restart the terminal and run expo start again

D. Change the app name in app.json

Solution

1. Step 1: Identify common cause of missing QR code

   Sometimes the terminal or Expo server glitches; restarting fixes this.

2. Step 2: Evaluate other options

   Deleting node_modules or uninstalling Expo is unnecessary and disruptive. Changing app name won't fix QR code display.

3. Final Answer:

   Restart the terminal and run expo start again -> Option C

4. Quick Check:

   Restart terminal to fix QR code [OK]

Hint: Restart terminal if QR code missing after expo start [OK]

Common Mistakes:

• Deleting important folders unnecessarily
• Uninstalling Expo CLI by mistake
• Changing config unrelated to QR code

5. You want to share your React Native app instantly with a friend using Expo Go. Which steps should you follow?

hard

A. Publish app to App Store before sharing

B. Run expo start, share the QR code link, friend scans with Expo Go app

C. Send JavaScript files via email, friend runs them locally

D. Build APK, send APK file, friend installs manually

Solution

1. Step 1: Use Expo Go sharing feature

   Running expo start generates a QR code and link to share instantly.

2. Step 2: Friend scans QR code with Expo Go

   The friend opens the app by scanning the code, no build or install needed.

3. Step 3: Eliminate other options

   Building APK or publishing is slower and not needed for quick sharing. Sending JS files won't run directly.

4. Final Answer:

   Run expo start, share the QR code link, friend scans with Expo Go app -> Option B

5. Quick Check:

   expo start + QR code = instant sharing [OK]

Hint: Share QR code from expo start for instant app access [OK]

Common Mistakes:

• Thinking APK build is needed for sharing
• Trying to send raw code files
• Assuming App Store publishing is required