Fallback UI patterns in React - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a fallback UI in React?

A fallback UI is a simple interface shown temporarily while the main content is loading or when an error occurs. It helps keep the app user-friendly by showing something instead of a blank screen.

beginner

How does React's <Suspense> component help with fallback UI?

<Suspense> lets you specify a fallback UI to show while waiting for some code or data to load. Once loading finishes, it shows the real content automatically.

intermediate

What is the purpose of an error boundary in fallback UI patterns?

An error boundary catches errors in child components and shows a fallback UI instead of crashing the whole app. This keeps the app stable and user-friendly.

beginner

Why is it important to keep fallback UIs simple and fast?

Fallback UIs should be simple and quick to show so users don’t wait long and don’t get confused. It improves the feeling of a smooth app experience.

beginner

Name two common fallback UI patterns in React.

1. Using <Suspense> with a loading spinner or message. 2. Using error boundaries to show an error message or alternative UI when something breaks.

What does React's <Suspense> component do?

A Manages global app state

B Shows a fallback UI while waiting for code or data to load

C Catches JavaScript errors in components

D Handles user input events

is designed to show fallback content while waiting for lazy-loaded components or data.

What is the main role of an error boundary?

A To style components

B To load components lazily

C To show a fallback UI when a child component throws an error

D To manage API calls

Error boundaries catch errors in their child components and display fallback UI instead of crashing.

Which of these is NOT a good practice for fallback UIs?

A Provide clear feedback to users

B Keep them simple and fast

C Use a spinner or loading message

D Show detailed app content immediately

Fallback UIs should be simple placeholders, not full app content, to keep loading fast and clear.

When should you use fallback UI patterns?

A While waiting for data or code to load, or when errors happen

B Only when styling components

C To handle user authentication

D To optimize images

Fallback UIs help during loading or error states to improve user experience.

Which React feature helps you show fallback UI during lazy loading?

A <Suspense>

B <ErrorBoundary>

C <useState>

D <useEffect>

is the React component designed for fallback UI during lazy loading.

Explain how fallback UI patterns improve user experience in React apps.

Think about what users see when data or code is not ready yet.

Describe how you would implement a fallback UI using React's Suspense and error boundaries.

Combine two React features to handle loading and errors.