StyleSheet.create in React Native - Practice Problems & Coding Challenges

Challenge - 5 Problems

📝 Syntax

intermediate

What is the output of this code snippet using StyleSheet.create?

Consider this React Native code snippet:

import { StyleSheet } from 'react-native';

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: 'blue'
  }
});

console.log(typeof styles.container);

What will be logged to the console?

React Native

import { StyleSheet } from 'react-native';

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: 'blue'
  }
});

console.log(typeof styles.container);

A "undefined"

B "string"

C "object"

D "function"

💡 Hint

Think about what StyleSheet.create returns for each style key.

StyleSheet.create returns an object where each key is a style reference object, so typeof styles.container is 'object'.

❓ ui_behavior

intermediate

Which option correctly applies a style created with StyleSheet.create?

Given this style:

const styles = StyleSheet.create({
  text: {
    color: 'red',
    fontSize: 20
  }
});

Which of these React Native Text components will render the text in red color and font size 20?

React Native

const styles = StyleSheet.create({
  text: {
    color: 'red',
    fontSize: 20
  }
});

A <Text style={styles.text}>Hello</Text>

B <Text style="styles.text">Hello</Text>

C <Text style={{styles.text}}>Hello</Text>

D <Text style={[styles.text]}>Hello</Text>

💡 Hint

Remember how to pass a style object in JSX.

The style prop expects an object or array of objects, so style={styles.text} is correct. Passing a string or double braces is incorrect.

❓ lifecycle

advanced

What happens if you create a new StyleSheet inside a component's render method?

Consider this React Native component:

function MyComponent() {
  const styles = StyleSheet.create({
    box: { width: 100, height: 100, backgroundColor: 'green' }
  });
  return ;
}

What is the impact of creating the StyleSheet inside the component function?

React Native

function MyComponent() {
  const styles = StyleSheet.create({
    box: { width: 100, height: 100, backgroundColor: 'green' }
  });
  return <View style={styles.box} />;
}

A The style is cached and reused automatically, no performance impact.

B A new style object is created on every render, which can hurt performance.

C The app will crash because StyleSheet.create cannot be called inside components.

D The style will not apply because it is created inside the component.

💡 Hint

Think about how often the component renders and what happens each time.

Calling StyleSheet.create inside the component creates a new style object each render, which can cause unnecessary work and reduce performance.

❓ navigation

advanced

How does StyleSheet.create affect dynamic styling during navigation transitions?

You have two screens in a React Native app. Each screen uses StyleSheet.create to define styles. If you want to change a style dynamically during navigation (like changing background color based on route params), which approach works best?

A Use StyleSheet.create for static styles and inline styles or state for dynamic changes.

B Modify the StyleSheet object directly to update styles dynamically.

C Recreate the StyleSheet inside the navigation listener to update styles.

D Use only inline styles and avoid StyleSheet.create for navigation styling.

💡 Hint

StyleSheet.create is for fixed styles, think about how to handle changes.

StyleSheet.create is optimized for static styles. For dynamic changes, use inline styles or state variables combined with styles.

🔧 Debug

expert

Why does this StyleSheet.create code cause a runtime error?

Look at this code:

const styles = StyleSheet.create({
  button: {
    backgroundColor: 'blue',
    padding: 10,
    borderRadius: '5'
  }
});

When applying styles.button, the app crashes. What is the cause?

React Native

const styles = StyleSheet.create({
  button: {
    backgroundColor: 'blue',
    padding: 10,
    borderRadius: '5'
  }
});

A padding must be a string with units like '10px', not a number.

B backgroundColor cannot be a string, it must be a number.

C StyleSheet.create does not support borderRadius property.

D borderRadius must be a number, not a string; '5' causes a runtime error.

💡 Hint

Check the data types expected for style properties.

React Native style properties like borderRadius expect numbers, not strings. Using '5' (string) causes a runtime error.