React's Exciting New Animation Features: View Transitions and Activity

React has introduced experimental support for View Transitions and Activity, significantly enhancing animation capabilities within the framework. View Transitions simplifies adding animations to UI transitions by declaratively defining what to animate. It leverages the new startTransition, useDeferredValue, and Suspense APIs for smooth animations, utilizing browser CSS for animation execution. It's particularly useful for animations in navigation, expanding elements, opening components, or re-ordering lists.

Activity is another exciting addition. This API efficiently hides and shows parts of the UI, allowing developers to deprioritize components without the performance overhead of unmounting or relying solely on CSS. When hidden, components are unmounted but retain their state, ready for a seamless re-appearance. This is great for optimizing performance by pre-rendering components likely to be used next or preserving state in less active UI sections.

Additionally, the release candidate for the React Compiler is available. This build-time tool optimizes React apps via automatic memoization. Case studies from Sanity Studio and Wakelet showcase the performance improvements achieved with the React Compiler.