10 Common React Mistakes Developers Made in 2022 (And How to Fix Them)


Published at: December 28, 2022

React is an incredible JavaScript library for building user interfaces, but like any technology, it’s easy to make mistakes, especially as React evolves and new features are added. In this blog post, we’ll walk through some of the most common mistakes React developers made in 2022 and how to avoid them to improve performance, readability, and maintainability.


1. Forgetting to Optimize Component Re-renders

The Mistake:

React components re-render by default whenever their state or props change. However, sometimes components are unnecessarily re-rendered when they don’t need to be. This can lead to performance issues, especially in larger applications.

The Fix:

  • React.memo: Wrap functional components with React.memo to prevent unnecessary re-renders. This memoizes the result and only re-renders when props change.
  • useCallback: Use useCallback to memoize functions passed as props to avoid causing unnecessary re-renders.
  • useMemo: Use useMemo to memoize expensive calculations that don’t need to be recomputed on every render.

By optimizing your components and preventing unnecessary re-renders, you can drastically improve the performance of your application.


2. Overusing useState for Derived State

The Mistake:

A common mistake is using useState to store data that can be derived from other state or props. This can lead to unnecessary complexity and stale data.

The Fix:

Avoid using useState for values that don’t need to be explicitly stored. Instead, calculate values on the fly using functions inside the render method or in useMemo.

// Bad: Storing derived state in useState
const [fullName, setFullName] = useState('');

// Good: Deriving value from props or state directly
const fullName = `${firstName} ${lastName}`;

By reducing unnecessary state and relying on derived values, you’ll keep your app simpler and easier to maintain.


3. Using useEffect for API Calls Instead of useQuery or React Query

The Mistake:

In 2022, many developers were still using useEffect to fetch data from APIs. This approach can lead to redundant network requests, manual loading/error handling, and poor performance.

The Fix:

Instead of using useEffect for API calls, use data fetching libraries like React Query or SWR. These libraries handle caching, background data updates, and error states, allowing you to focus on building your UI.

// Using React Query for API calls
const { data, error, isLoading } = useQuery('posts', fetchPosts);

These libraries offer a much cleaner and more efficient way of managing async data.


4. Not Using Context API Properly for Global State Management

The Mistake:

Some developers misuse React Context API for global state management by placing too much logic inside context providers, leading to performance bottlenecks and difficult-to-maintain code.

The Fix:

For global state, use context sparingly. Keep the logic inside context providers minimal. For more complex state management, consider using dedicated state management libraries like Redux, Recoil, or Zustand.

// Avoid putting too much logic in the context provider
const Context = React.createContext();

const Provider = ({ children }) => {
  const value = useMyComplexLogic();
  return <Context.Provider value={value}>{children}</Context.Provider>;
};

This approach keeps your components clean and minimizes unnecessary re-renders caused by context value changes.


5. Not Handling Error Boundaries

The Mistake:

React doesn’t handle errors in the component tree by default, which can lead to unhandled exceptions and a broken user interface.

The Fix:

Implement Error Boundaries to gracefully handle errors in the UI and provide fallback content. This ensures that the rest of the application continues to function even if one component fails.

class ErrorBoundary extends React.Component {
  state = { hasError: false };

  static getDerivedStateFromError(error) {
    return { hasError: true };
  }

  render() {
    if (this.state.hasError) {
      return <h1>Something went wrong.</h1>;
    }
    return this.props.children;
  }
}

By using error boundaries, you ensure that errors don’t break your whole application.


6. Directly Modifying State or Props

The Mistake:

Mutating state or props directly is a common mistake that can lead to unpredictable behavior, especially in larger apps. This can cause unexpected re-renders or inconsistent UI updates.

The Fix:

Always treat state and props as immutable. Use state updater functions to make changes to state and avoid direct mutation.

// Bad: Mutating state directly
state.items.push(newItem);

// Good: Using updater function for state
setState((prevState) => [...prevState.items, newItem]);

By following immutability principles, you ensure that React’s state management system works as expected.


7. Ignoring Key Prop in Lists

The Mistake:

A common performance issue occurs when keys are not used correctly in lists. This can cause React to re-render entire lists unnecessarily instead of just updating the modified items.

The Fix:

Always provide a unique and stable key for each element in a list to allow React to efficiently update the list. This helps React keep track of items and avoid unnecessary re-renders.

// Bad: Missing keys or using indexes
{items.map((item, index) => (
  <div key={index}>{item}</div>
))}

// Good: Using a unique identifier as the key
{items.map((item) => (
  <div key={item.id}>{item.name}</div>
))}

This small change can significantly improve rendering performance.


8. Not Using Lazy Loading for Components

The Mistake:

Large React applications often have performance problems because all the components are loaded at once, even if the user doesn’t need them immediately.

The Fix:

Use React.lazy and Suspense to load components dynamically as needed. This can drastically reduce the initial load time by splitting your code into smaller chunks.

// Lazy load a component
const MyComponent = React.lazy(() => import('./MyComponent'));

<Suspense fallback={<Loading />}>
  <MyComponent />
</Suspense>

By implementing lazy loading, you can improve the performance of your React application and provide a smoother user experience.


9. Not Memoizing Functions and Values in Props

The Mistake:

Passing non-memoized functions or values as props can lead to unnecessary re-renders of child components. This can be especially problematic for deeply nested components.

The Fix:

Use useMemo and useCallback to memoize values and functions before passing them down to child components.

const memoizedValue = useMemo(() => expensiveComputation(a, b), [a, b]);
const memoizedCallback = useCallback(() => handleEvent(a, b), [a, b]);

Memoizing functions and values ensures that your child components don’t re-render unnecessarily.


10. Not Keeping the UI State and Business Logic Separate

The Mistake:

Mixing UI-related state with business logic or side effects can create hard-to-maintain and test code. This can lead to tight coupling and unexpected behavior.

The Fix:

Separate UI state from business logic by using hooks and reducers for managing complex state or side effects. useReducer is a great option for handling complex state in functional components.

// Example of using useReducer for business logic
const initialState = { count: 0 };
const reducer = (state, action) => {
  switch (action.type) {
    case 'increment':
      return { count: state.count + 1 };
    default:
      return state;
  }
};

const Counter = () => {
  const [state, dispatch] = useReducer(reducer, initialState);
  return (
    <button onClick={() => dispatch({ type: 'increment' })}>
      Count: {state.count}
    </button>
  );
};

By keeping logic and UI state separate, your components remain more modular and easier to manage.


Conclusion

React is constantly evolving, and while it’s easy to make mistakes along the way, understanding the best practices can help you avoid common pitfalls. By optimizing performance, improving state management, and following React’s best practices, you’ll write cleaner, more maintainable code in 2022 and beyond.

Now that you’re aware of the most common React mistakes and how to fix them, you’re ready to build faster, more efficient applications!


Hope you find this helpful!

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