Suspense and Transitions Quiz

Question 1

What does a Suspense boundary do?

Accepted Answer

Shows a fallback while something in its subtree is not ready

Answer

Catches errors thrown by its children

Answer

Delays rendering by a fixed time

Answer

Retries failed network requests

Question 2

Why does a plain fetch inside useEffect not trigger Suspense?

Accepted Answer

Suspense requires something to suspend, and a plain fetch does not integrate with that mechanism

Answer

Effects run too late

Answer

fetch is not supported in React

Answer

The component must be lazy

Question 3

What is wrong with calling lazy inside a component body?

Accepted Answer

A new component type is created on every render, so the subtree remounts and refetches

Answer

lazy cannot be called in a function

Answer

The import runs twice

Answer

It only works with named exports

Question 4

What does a module loaded with lazy need?

Accepted Answer

A default export

Answer

A named export matching the component

Answer

A .lazy.js file extension

Answer

To be registered in the router

Question 5

What does startTransition do to a state update?

Accepted Answer

Marks it as non-urgent so React can interrupt it to handle urgent updates first

Answer

Delays it by a fixed number of milliseconds

Answer

Runs it in a web worker

Answer

Batches it with other updates

Question 6

When would you use useDeferredValue instead of useTransition?

Accepted Answer

When you receive a value but do not control the state update that produced it

Answer

When the update is urgent

Answer

When the component is lazy loaded

Answer

When you need a loading spinner

Question 7

What happens when an update inside startTransition causes a component to suspend?

Accepted Answer

React keeps showing the current content until the new one is ready

Answer

The Suspense fallback replaces the content immediately

Answer

The transition is cancelled

Answer

An error is thrown

Question 8

Which action is a poor candidate for an optimistic update?

Accepted Answer

Processing a payment

Answer

Liking a post

Answer

Toggling a checkbox

Answer

Adding a comment