The Ultimate Code Review Checklist

Code reviews are an essential part of software development. They ensure code quality, maintainability, and adherence to best practices. This checklist will help you perform thorough and effective code reviews, covering general coding principles, React-specific guidelines, performance considerations, and more.

General Best Practices

1. Does the code work as expected? Ensure there are no runtime errors or unexpected behavior.
2. Is the project status clearly documented? README or inline documentation should indicate the code’s purpose and current state.
3. Is the code easy to understand? A fresh developer should be able to grasp its logic quickly.
4. Does it follow coding standards? Ensure consistency with React and project guidelines.
5. Is the code aligned with existing patterns? Stick to established conventions to maintain uniformity.
6. Avoid duplication (DRY principle). If the same logic appears multiple times, refactor it.
7. Is the code testable? Components and functions should be easy to test.
8. Are functions, classes, and components appropriately sized? Keep them small and single-responsibility.
9. Are event listeners cleaned up properly? Prevent memory leaks by removing event listeners when components unmount.
10. Follow proper naming conventions. Ensure consistent variable, file, and translation naming.
11. Are unused dependencies removed? Keep package.json clean.
12. Maintain a clear separation of concerns. Organize the code logically.

Code Style & Readability

1. No hardcoded values. Use constants instead.
2. Avoid excessive if/else nesting. Use early returns or switch statements when appropriate.
3. Remove commented-out code. Keep the repository clean.
4. Limit unnecessary comments. Comments should explain ‘why’ rather than ‘how’.
5. Include meaningful comments where necessary. Complex logic should have explanatory notes.

Modern JavaScript (ES6/7+)

1. Use modern ES6+ features. Write concise, maintainable code.
2. Prefer arrow functions over function expressions where applicable. Maintain consistency.
3. Use the spread/rest operator. Avoid unnecessary array mutations.
4. Set default function parameters. Prevent errors from missing arguments.
5. Use const over let whenever possible. Avoid var entirely.
6. Use module imports and exports. Stick to ES modules.
7. Utilize template literals. Improve string concatenation readability.
8. Apply destructuring assignments. Enhance code clarity.
9. Handle promises properly. Ensure async/await rejections are caught.

React Code Review

1. Are PropTypes or TypeScript types defined? Ensure proper type checking.
2. Are components small and reusable? Follow the Single Responsibility Principle.
3. Use functional components where applicable. Prefer hooks over class components.
4. Avoid API calls in components. Delegate to services or middleware (e.g., Redux Saga).
5. No direct state modifications in loops. Use setState or useState correctly.
6. Remove unnecessary constructors in class components. Use functional components instead.
7. Keep logic out of the render method. Separate concerns appropriately.
8. Avoid mixins. Prefer higher-order components (HOCs) or hooks for reuse.

Third-Party Libraries

1. Leverage utility libraries like Lodash or Ramda. Avoid reinventing the wheel.
2. Ensure proper use of Immutable.js (if applicable). Prevent unintended state mutations.
3. Explore useful libraries. Is there a better tool available for the task?

Linting & Static Code Analysis

1. No ESLint errors or warnings. Keep the codebase clean.
2. Remove unnecessary console logs. Use proper logging mechanisms for debugging.

CSS & Styling

1. Follow a consistent CSS methodology. (e.g., BEM, SMACSS, OOCSS)
2. Use minimal selector specificity. Keep styles maintainable.
3. Use CSS-in-JS appropriately. If applicable, ensure best practices are followed.
4. Use hex color codes (e.g., #000). Prefer rgba() when transparency is needed.
5. Avoid absolute positioning unless necessary. Use flexbox or grid instead.
6. Utilize flexbox for layout consistency.
7. Minimize the use of !important. This indicates poor CSS structure.
8. Avoid animating width, height, top, left, etc. Use transform for better performance.
9. Use consistent units (e.g., px, rem, em). Stick to a unified unit system.
10. Avoid inline styles unless dynamic styling is required. Prefer external stylesheets or CSS modules.

Testing & Quality Assurance

1. Are tests clear, maintainable, and effective? Keep tests reliable.
2. Are test names descriptive and meaningful? Make tests self-explanatory.
3. Avoid logic in tests. Tests should be straightforward.
4. Test one thing per test case. Keep them focused.
5. Cover edge cases. Don’t just test the happy path.
6. Test behavior, not implementation details. Prevent fragile tests.
7. Use mocks and stubs appropriately. Simulate dependencies correctly.

Git Best Practices

1. Are commits small and logically structured? Make them meaningful.
2. Do commit messages follow a clear pattern? Use concise, descriptive messages.
3. Use branches for new features. Avoid committing directly to main.
4. Ensure no unwanted files are committed. Use .gitignore to exclude unnecessary files.

Conclusion

By following this checklist, you can ensure that your code is clean, maintainable, and aligned with best practices. A thorough code review helps the entire team produce better software and reduces technical debt in the long run.

Additional Resources

• Code Review Checklist – Effective Code Reviews
• React Code Review Checklist
• Checklist for Reviewing Your Own React Code
• Front-End Code Review & Validation Tools
• A Guide to Unit Testing in JavaScript
• Unit Testing Checklist