Boosting React app performance is crucial for a positive user experience. This article outlines seven proven performance patterns gleaned from optimizing numerous production React applications.

1. Memoization with useMemo and useCallback:

Problem: Unnecessary re-renders due to unchanged props or state.

Solution: Cache computationally expensive operations and function references.

const ExpensiveComponent = ({ items }) => {
  const sortedList = useMemo(() => items.sort((a, b) => a.price - b.price), [items]);
  const handleClick = useCallback(() => {
    console.log('Item clicked:', sortedList[0]);
  }, [sortedList]);
  return ;
};

Best Practices: Use with React.memo for child components to prevent unnecessary subtree updates. Ideal for complex calculations (sorting, filtering), callbacks passed to optimized children, and stable context provider values.

2. Lazy Loading and Code Splitting:

Problem: Large initial bundle size impacting First Contentful Paint (FCP).

Solution: Dynamic imports and Suspense for on-demand loading.

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

const Dashboard = () => (
  }>
    {showCharts && }
  
);

Advanced: Integrate with React Router for route-based code splitting.

3. Virtualized Lists for Large Datasets:

Problem: Rendering thousands of items overwhelms the DOM.

Solution: react-window renders only visible items.

import { FixedSizeList } from 'react-window';

const BigList = ({ items }) => (
  
    {({ index, style }) => (
      
...
    )}
  
);

Bonus: Use VariableSizeList for dynamic row heights and react-virtualized-auto-sizer for responsive containers.

4. Efficient State Management:

Problem: Multiple state updates causing cascading re-renders.

Solution: Leverage React 18's automatic batching.

React 18 :

setCount(1);
setText('Updated'); // Single re-render

Pre-React 18 or for complex scenarios: Use useReducer for atomic state updates.

5. Debouncing API Calls:

Problem: Excessive API requests from rapid user input (e.g., search bars).

Solution: A custom useDebounce hook.

import { useEffect, useState } from 'react';

const useDebouncedValue = (value, delay) => {
  const [debouncedValue, setDebouncedValue] = useState(value);
  useEffect(() => {
    const handler = setTimeout(() => setDebouncedValue(value), delay);
    return () => clearTimeout(handler);
  }, [value, delay]);
  return debouncedValue;
};

Pro Tip: Combine with AbortController to cancel pending requests.

6. Optimized Context API:

Problem: Unnecessary re-renders of context consumers due to unrelated changes.

Solution: Split contexts and memoize provider values.

7. Optimistic UI Updates:

Problem: Slow UI due to waiting for API responses.

Solution: Provide immediate visual feedback and rollback on error.

Performance Checklist:

1. Profile re-renders with React DevTools Profiler.
2. Analyze bundle size with source-map-explorer.
3. Test with Chrome's Performance tab (CPU throttling).
4. Use React.memo, useMemo, useCallback strategically.
5. Implement incremental loading.
6. Optimize images/media with lazy loading.
7. Consider server-side rendering for critical content.

Remember: Profile first, optimize second! These techniques are applicable across various React frameworks (Next.js, Gatsby, etc.).