React Performance Optimization

Understanding React Performance

Performance optimization in React isn't about premature optimization—it's about understanding when and why components re-render, and how to prevent unnecessary work.

React.memo for Component Memoization

React.memo prevents re-renders when props haven't changed. Wrap your component to memoize its output:

const MyComponent = React.memo(({ data }) => {
  return 
{data.name}
})

useMemo and useCallback Hooks

useMemo caches expensive computations, while useCallback memoizes function references to prevent child re-renders:

const expensiveValue = useMemo(() => {
  return computeExpensiveValue(a, b)
}, [a, b])

const handleClick = useCallback(() => {
  doSomething(a, b)
}, [a, b])

Code Splitting with React.lazy

Split your application into smaller chunks that load on demand, reducing initial bundle size:

const HeavyComponent = React.lazy(() => import('./HeavyComponent'))

function App() {
  return (
    }>
      
    
  )
}

Virtualization for Long Lists

Use libraries like react-window or react-virtualized to render only visible items in long lists, dramatically improving performance.

Avoid Inline Functions and Objects

Creating functions or objects inline in JSX causes new references on every render. Extract them outside the component or use useCallback/useMemo.

Profiling with React DevTools

Use the React DevTools Profiler to identify performance bottlenecks. Record a session, interact with your app, and analyze which components are rendering unnecessarily.

Key Takeaways

• Measure before optimizing
• Focus on components that render frequently
• Use production builds for accurate testing
• Consider the user experience impact

Performance optimization is a journey. Start with the basics, measure your improvements, and iterate based on real user data.