What are the best practices for using React's Concurrent Mode?

What are the best practices for using React's Concurrent Mode?

When using React's Concurrent Mode, it's important to focus on optimizing rendering performance and user experience. Here are some best practices:

1. Use Suspense: Leverage Suspense for data fetching to improve loading states.
2. Prioritize Updates: Use startTransition to mark updates that can be interrupted, allowing for smoother user interactions.
3. Avoid Blocking the Main Thread: Keep heavy computations off the main thread to prevent UI jank.
4. Break Down Components: Split large components into smaller ones to take advantage of concurrent rendering.

Can you explain how Suspense works in Concurrent Mode?

Sure! Suspense allows you to defer rendering part of your component tree until some condition is met, such as data being loaded. You can wrap components that need to wait for data in a <Suspense> component and provide a fallback UI, like a loading spinner. This way, while the data is being fetched, the user sees a loading state instead of a blank screen.

What are some common pitfalls to avoid when using Concurrent Mode?

Some common pitfalls include:

1. Overusing startTransition: Use it judiciously; not every update needs to be marked as a transition.
2. Neglecting Error Boundaries: Ensure you have error boundaries in place to catch errors in async components.
3. Ignoring Performance Metrics: Monitor performance to identify bottlenecks and optimize accordingly.

How can I test components that use Concurrent Mode?

Testing components in Concurrent Mode can be done using libraries like React Testing Library. You can simulate user interactions and check for loading states and final outputs. Make sure to account for async behavior in your tests, using waitFor or similar utilities to handle the asynchronous nature of Concurrent Mode.