React's declarative model simplifies development but can hide performance issues until applications grow. Slow initial loads, janky interactions, and excessive re-renders frustrate users. Systematic profiling identifies bottlenecks, while React's optimization APIs address specific issues.
Identifying Re-render Issues
React DevTools Profiler visualizes component renders and their causes. Unexpected re-renders often trace to unstable references—inline objects, arrays, or functions recreated each render. Context changes triggering tree-wide re-renders indicate overly broad context usage.
- Use React.memo for expensive components that receive stable props
- Stabilize callbacks with useCallback when passed to memoized children
- Apply useMemo for expensive computations not needed every render
- Split context providers to limit re-render scope
- Consider state management libraries for complex shared state
Bundle Optimization
Large JavaScript bundles delay time-to-interactive. Code splitting with React.lazy loads features on demand. Tree shaking eliminates unused code when imports are specific. Bundle analyzers visualize what contributes to size, often revealing surprising dependencies worth replacing or removing.