Only the parts of the DOM that have changed

During reconciliation, React updates which parts of the DOM?

This test assesses knowledge of key features, hooks, directives, and concepts introduced in React 19, including Server Actions, directives, hooks, and Virtual DOM mechanisms.

To send data from client to server and integrate client and server components

What is the primary purpose of actions in React 19?

They attach functions to the form's action attribute to handle submissions on the server

They convert forms into client-only components

How do Server Actions interact with HTML forms in React 19?

Which of the following is NOT a feature introduced in React 19?

To apply temporary UI updates while awaiting server responses

To optimize rendering performance by memoizing components

To manage routing state in single-page applications

To automatically fetch data without manual calls

What is the purpose of the useOptimistic hook in React 19?

Automatic re-rendering of only necessary UI parts upon state changes, reducing the need for useCallback or useMemo

Converting React code to vanilla JavaScript

Replacing the JavaScript engine in browsers

What advantage does the React Compiler provide in React 19?

Declaring server-side async functions callable from client components

What is the 'use server' directive used for in React 19?

Which process in React describes identifying differences between Virtual DOM trees?

It fetches data from the server automatically

It updates state based on the result of a form action

It replaces useEffect and useContext hooks

Which statement about the 'useFormState' hook is TRUE?

Which hooks are related to form handling in React 19?

'use server' must be at the very beginning of the function or module

'use server' can be used on any function, synchronous or asynchronous

Which rule is NOT correct when using the 'use server' directive?

Status of the last form submission including pending state and submitted form data

What information does the useFormStatus hook provide?

npm install react@experimental and npm install react-dom@experimental

How can you install the React experimental version matching React 19?

Place it at the very top of a file, above all imports, enclosed in single or double quotes

What is the correct way to use the 'use client' directive in React 19?

It can be called conditionally and in loops, replacing useContext in some contexts

How does the use hook differ from useContext in React 19?

A direct manipulation of the browser’s real DOM

An in-memory representation of the real DOM used to optimize updates

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