How to Increase and Optimize Performance in a React Application

Performance optimization is a crucial part of building modern, scalable React applications. A fast, smooth UI boosts user experience and retention, especially as your app grows in size and complexity. This article dives into best practices and strategies to improve the performance of your React applications.

1. Use React's Built-in Memoization
React provides several built-in tools to prevent unnecessary re-renders:

🔹 React.memo()
Use this to wrap functional components so that they only re-render when props change.jsx

const MyComponent = React.memo(({ value }) => {
  return <div>{value}</div>;
});

🔹 useMemo() and useCallback()
Use these to memoize functions and computed values inside your components.

const expensiveValue = useMemo(() => computeExpensiveValue(data), [data]);
const handleClick = useCallback(() => doSomething(), []);

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2. Code Splitting with React.lazy and Suspense
Code splitting helps load parts of your app only when needed, reducing initial load time.

const LazyComponent = React.lazy(() => import('./LazyComponent'));

function App() {
  return (
    <Suspense fallback={<div>Loading...</div>}>
      <LazyComponent />
    </Suspense>
  );
}

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3. Bundle Optimization
Reduce the final bundle size by:

• Removing unused dependencies
• Using tree-shaking
• Importing only what you use from libraries like Lodash or Material-UI

// Bad
import _ from 'lodash';

// Good
import debounce from 'lodash/debounce';

Use tools like:

• Webpack Bundle Analyzer
• Source Map Explorer

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4. Virtualise Long Lists
Rendering long lists can be expensive. Libraries like react-window or react-virtualized render only the visible items.

import { FixedSizeList as List } from 'react-window';

<List
  height={300}
  itemCount={1000}
  itemSize={35}
  width={300}
>
  {({ index, style }) => <div style={style}>Item {index}</div>}
</List>

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5. Avoid Anonymous Functions in JSX
Defining functions inline in JSX can cause unnecessary re-renders.

// ❌ Not optimal
<button onClick={() => doSomething()}>Click me</button>

// ✅ Better
const handleClick = () => doSomething();
<button onClick={handleClick}>Click me</button>

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6. Minimize Re-renders
Use tools like:
React.memo()
shouldComponentUpdate (class components)
Profiling with React DevTools to identify unnecessary renders

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1. Use the Profiler API React DevTools has a Profiler tab to visualize rendering performance.
2. Find which components render frequently
3. Optimize or memoize them
4. Remove redundant state or context updates

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8. Use Server-side Rendering (SSR) or Static Site Generation (SSG)
Frameworks like Next.js provide SSR and SSG capabilities to improve time-to-first-byte and SEO.

// pages/index.tsx in Next.js
export async function getStaticProps() {
  const data = await fetchData();
  return { props: { data } };
}

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9. Use Efficient State Management
Large global state trees can cause performance issues.

• Use React Context wisely (avoid passing large data)
• Use lightweight state libraries like Zustand, Jotai, or Recoil
• For large apps, consider Redux Toolkit with createSlice for optimized patterns

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10. Lazy Load Images and Components
Use libraries like:

• react-lazyload
• Native loading="lazy" for images

<img src="/image.jpg" loading="lazy" alt="example" />

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Conclusion
Optimizing a React application is about balancing performance, maintainability, and scalability. Start by profiling your app, identifying bottlenecks, and applying these techniques selectively. With thoughtful optimization, your React app can remain snappy and delightful even as it grows.