Which statement about rendering in React is true?

Which statement about rendering in React is true?

• A. The virtual DOM is rendered directly to the screen without any diffing.
• B. React computes changes by diffing the new virtual DOM against the previous version and updating only the changed parts.
• C. JSX is only a syntax sugar with no runtime representation.
• D. State changes do not trigger any DOM updates.

Answer: (B)

Rendering in React hinges on a virtual DOM and a reconciliation process. When state or props change, React builds a new virtual DOM tree and diffing it against the previous tree to determine what actually changed. It then updates only the parts of the real DOM that differ. This selective updating is what makes rendering efficient. That approach is exactly what the correct statement describes: changes are computed by diffing the new virtual DOM against the previous version, and only the changed parts are updated in the real DOM. The other ideas don’t fit: the virtual DOM isn’t rendered directly to the screen without diffing, JSX isn’t just purely decorative syntax with no runtime form—JSX compiles to React elements and is used to construct the virtual DOM at runtime—and state changes do trigger re-renders, which then lead to DOM updates through this diffing process.

Rendering in React hinges on a virtual DOM and a reconciliation process. When state or props change, React builds a new virtual DOM tree and diffing it against the previous tree to determine what actually changed. It then updates only the parts of the real DOM that differ. This selective updating is what makes rendering efficient.

That approach is exactly what the correct statement describes: changes are computed by diffing the new virtual DOM against the previous version, and only the changed parts are updated in the real DOM.

The other ideas don’t fit: the virtual DOM isn’t rendered directly to the screen without diffing, JSX isn’t just purely decorative syntax with no runtime form—JSX compiles to React elements and is used to construct the virtual DOM at runtime—and state changes do trigger re-renders, which then lead to DOM updates through this diffing process.