React.js ecosystem including hooks, state management, and component patterns.
The virtual DOM is a lightweight JavaScript representation of the real DOM that React uses to optimize rendering performance.
You can use controlled components with useState, uncontrolled components with refs, or form libraries like React Hook Form for complex needs.
Hooks are functions that let you use state and other React features in functional components without writing classes.
Keys help React identify which items have changed, been added, or removed, enabling efficient updates to the DOM.
The cleanup function in useEffect runs before the component unmounts and before re-running the effect, used to prevent memory leaks.
Options include lifting state up, Context API, or external state managers like Redux, Zustand, or Jotai depending on complexity.
Use React Testing Library for component tests focusing on user behavior, Jest for unit tests, and Playwright or Cypress for end-to-end tests.
Reconciliation is React's algorithm for diffing two trees to determine which parts need to be changed in the actual DOM.
Server Components run only on the server with zero client JavaScript, while Client Components run in the browser and can use hooks and interactivity.
Key techniques include memoization (memo, useMemo, useCallback), code splitting, virtualization for long lists, and avoiding unnecessary re-renders.
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