Native modules concept in React Native - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of native modules in React Native?

Native modules allow React Native apps to:

A Convert JavaScript code into native machine code automatically

B Replace JavaScript code with HTML for better UI

C Run React Native apps only on web browsers

D Access platform-specific features not available in JavaScript

💡 Hint

Think about what JavaScript alone cannot do on mobile devices.

Native modules let React Native apps use device features like camera or sensors by bridging JavaScript with native code.

❓ ui_behavior

intermediate

Which behavior occurs when a native module method is called from React Native JavaScript?

When JavaScript calls a native module method, what happens next?

A The app reloads the JavaScript bundle to apply native changes

B The call is sent asynchronously to native code, which executes and returns a result

C The native module replaces the entire React Native UI instantly

D The JavaScript code pauses and waits synchronously for native code to finish

💡 Hint

Think about how JavaScript and native code communicate without freezing the app.

Native module calls are asynchronous to keep the app responsive while native code runs.

❓ lifecycle

advanced

What happens if a native module is not properly registered in React Native?

If you forget to register a native module, what is the likely outcome when you try to use it?

A JavaScript throws an error saying the module is undefined or not found

B The native module runs but returns empty data silently

C The app crashes immediately on startup

D The native module works but with degraded performance

💡 Hint

Consider what happens when JavaScript tries to access something that does not exist.

If a native module is not registered, JavaScript cannot find it and throws an error.

❓ navigation

advanced

How can native modules affect navigation behavior in React Native apps?

Which statement best describes native modules' role in navigation?

A Native modules disable React Native navigation libraries when used

B Native modules automatically handle all navigation without JavaScript code

C Native modules can provide custom native navigation components that JavaScript can control

D Native modules only affect UI styling, not navigation

💡 Hint

Think about how native modules can extend app features beyond JavaScript.

Native modules can expose native navigation controls that React Native JavaScript can invoke for smoother or custom navigation.

🔧 Debug

expert

What error will occur if a native module method returns a wrong data type to JavaScript?

If a native module method returns a number but JavaScript expects a string, what happens?

A JavaScript receives the number without error but may behave unexpectedly

B React Native throws a type mismatch error and crashes the app

C The native module automatically converts the number to a string

D The app silently ignores the returned value and continues

💡 Hint

JavaScript is loosely typed but unexpected types can cause logic bugs.

JavaScript does not crash on type mismatches but may produce wrong results if types differ from expectations.