What does diffing refer to in React's virtual DOM?

What does diffing refer to in React's virtual DOM?

• A. Rendering updates directly to the actual DOM.
• B. Comparing the new virtual DOM with a pre-update version to identify changes.
• C. Serializing JSX to HTML strings.
• D. Removing unused DOM nodes from memory.

Answer: (B)

Diffing is the process React uses to reconcile the UI by comparing the updated virtual DOM tree with the previous one to figure out exactly what changed. When state or props update, React builds a new virtual DOM and then walks both trees to identify the minimal set of changes required to bring the real DOM up to date. This selective update is what makes React efficient, preventing unnecessary re-renders and DOM manipulations. The correct description fits this idea: it describes comparing the new virtual DOM with a prior version to identify changes. The other options describe different ideas—updating the real DOM directly would bypass diffing, serializing JSX to HTML strings isn’t about computing changes, and removing unused nodes is more about memory cleanup than calculating updates.

Diffing is the process React uses to reconcile the UI by comparing the updated virtual DOM tree with the previous one to figure out exactly what changed. When state or props update, React builds a new virtual DOM and then walks both trees to identify the minimal set of changes required to bring the real DOM up to date. This selective update is what makes React efficient, preventing unnecessary re-renders and DOM manipulations.

The correct description fits this idea: it describes comparing the new virtual DOM with a prior version to identify changes. The other options describe different ideas—updating the real DOM directly would bypass diffing, serializing JSX to HTML strings isn’t about computing changes, and removing unused nodes is more about memory cleanup than calculating updates.