Expo Go for quick start in React Native - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What happens when you scan an Expo Go QR code?

You scan a QR code generated by Expo Go for a React Native app. What is the immediate result on your phone?

A Nothing happens because Expo Go requires manual app installation first.

B Your phone opens the app store to download the app permanently.

C The Expo Go app downloads and runs the JavaScript bundle of the app instantly.

D The QR code opens a web page in the browser instead of running the app.

💡 Hint

Think about how Expo Go lets you preview apps without installing them.

Expo Go uses the QR code to fetch the JavaScript bundle from your development server and runs it inside the Expo Go app immediately.

🧠 Conceptual

intermediate

Why use Expo Go for quick start in React Native?

Which of these is the main advantage of using Expo Go when starting a React Native project?

A It automatically publishes your app to the app stores.

B It allows running your app on a device without building a native binary first.

C It replaces the need for writing JavaScript code.

D It requires no internet connection to run your app.

💡 Hint

Think about how Expo Go helps you test your app quickly on real devices.

Expo Go lets you run your React Native app on a phone instantly by loading the JavaScript bundle, skipping the native build step.

❓ lifecycle

advanced

What happens if you close Expo Go while your app is running?

If you close the Expo Go app on your phone while your React Native app is running inside it, what happens to your app?

A The app switches to a web version automatically.

B The app continues running in the background indefinitely.

C The app crashes and restarts automatically.

D The React Native app stops running immediately.

💡 Hint

Consider how mobile apps behave when their container app is closed.

Expo Go hosts your React Native app; closing Expo Go stops the app because it runs inside Expo Go.

❓ navigation

advanced

How to reload your app in Expo Go after code changes?

After editing your React Native code, how do you reload the app in Expo Go to see the changes?

A Shake the device and select 'Reload' from the developer menu.

B Close and reopen Expo Go app completely.

C Scan the QR code again to reload the app.

D Restart your computer to refresh the app.

💡 Hint

Expo Go has a developer menu accessible by a gesture.

Shaking the device opens the Expo developer menu where you can reload the app to see code changes.

📝 Syntax

expert

What error occurs if you run Expo Go without starting the development server?

You open Expo Go and scan the QR code, but the development server is not running. What error will Expo Go show?

A "Could not connect to development server" error message.

B "Syntax error in JavaScript code" message.

C "App installed successfully" message with blank screen.

D "App is running offline" message with full functionality.

💡 Hint

Think about what Expo Go needs to load your app code.

Expo Go needs the development server to serve the JavaScript bundle; if it's off, it shows a connection error.

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