React Developer Skill

Core React Concepts

Components and JSX

• Functional components with hooks
• Class components (legacy support)
• JSX syntax and best practices
• Props and prop validation with PropTypes/TypeScript

React Hooks Mastery

• useState: State management in functional components
• useEffect: Side effects and lifecycle management
• useContext: Context API for state sharing
• useReducer: Complex state management
• useMemo: Performance optimization with memoization
• useCallback: Function memoization
• useRef: DOM access and persistent values
• Custom Hooks: Reusable stateful logic

State Management Patterns

• Local State: useState, useReducer
• Context API: useContext for global state
• Redux: State management with Redux Toolkit
• Zustand: Lightweight state management
• Recoil: Facebook's state management library
• SWR/React Query: Server state management

Performance Optimization

• React.memo for component memoization
• useMemo and useCallback for expensive computations
• Code splitting with React.lazy and Suspense
• Virtual scrolling for large lists
• Bundle size optimization

Modern React Patterns

• Compound Components: Flexible component composition
• Render Props: Sharing component logic
• Higher-Order Components (HOCs): Component enhancement
• Custom Hooks Pattern: Reusable stateful logic
• State Reducer Pattern: Complex state updates
• Control Props Pattern: External component control

Styling Solutions

• CSS Modules: Scoped CSS
• Styled Components: CSS-in-JS
• Emotion: High-performance CSS-in-JS
• Tailwind CSS: Utility-first CSS
• CSS-in-JS best practices

Testing Strategies

• Jest: Testing framework
• React Testing Library: Component testing
• Enzyme: Component testing (legacy)
• Cypress: End-to-end testing
• Storybook: Component development and testing

React Ecosystem Tools

• Create React App: Quick start setup
• Vite: Fast build tool
• Next.js: Full-stack React framework
• Gatsby: Static site generator
• Remix: Full-stack web framework

Best Practices

1. Component Design: Single responsibility principle
2. Prop Drilling: Avoid with context or state management
3. Side Effects: Proper useEffect dependency management
4. Key Props: Correct usage in lists
5. Conditional Rendering: Best practices
6. Error Boundaries: Graceful error handling
7. Accessibility: ARIA attributes and semantic HTML

Common Pitfalls and Solutions

• Stale Closures: Proper dependency arrays
• Infinite Renders: Incorrect useEffect dependencies
• Memory Leaks: Cleanup functions in useEffect
• Prop Drilling: Use context or state management
• Unnecessary Re-renders: Memoization strategies

Migration and Upgrade Guides

• React Class to Functional: Migration strategies
• React 18 Features: Concurrent features, automatic batching
• Strict Mode: Development best practices

Code Examples

Custom Hook Example

import { useState, useEffect } from 'react';

function useFetch(url) {
  const [data, setData] = useState(null);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(null);

  useEffect(() => {
    async function fetchData() {
      try {
        const response = await fetch(url);
        const data = await response.json();
        setData(data);
      } catch (err) {
        setError(err);
      } finally {
        setLoading(false);
      }
    }

    fetchData();
  }, [url]);

  return { data, loading, error };
}

Performance Optimization Example

import React, { memo, useMemo, useCallback } from 'react';

const ExpensiveComponent = memo(({ items, onItemClick }) => {
  const processedItems = useMemo(() => {
    return items.map(item => ({
      ...item,
      processed: true,
      value: item.value * 2
    }));
  }, [items]);

  const handleClick = useCallback((item) => {
    onItemClick(item);
  }, [onItemClick]);

  return (
    <div>
      {processedItems.map(item => (
        <div key={item.id} onClick={() => handleClick(item)}>
          {item.value}
        </div>
      ))}
    </div>
  );
});

When working with React projects, always consider:

• Component reusability and composition
• Performance implications of state changes
• Accessibility requirements
• Testing strategies
• Bundle size impact
• SEO considerations for server-rendered apps