Code review plays a crucial role in any product development process by ensuring:

• Code quality
• Maintainability
• A shared understanding of the application among team members

This checklist, focused on JavaScript/React, helps perform effective code reviews and is also useful for self-reviews before raising a pull request.

Before Diving into the Checklist

Keep the following in mind:

• Understand the Context
  • Always read the change-set or pull request (PR) description to understand what problem the code is solving or what functionality it delivers.
• Handle Large PR's Strategically
  • For larger PR's, begin with a functional review. This will help in understanding the overall flow, making the code review process more effective.
• Provide Constructive Feedback
  • Feedback should focus on improving the product, not individuals.
    Maintain a collaborative tone—ask questions or suggest alternatives when something seems off. The goal is to enhance code quality and encourage team growth.
    
    

Code Review Checklist

1. Code Comprehensibility
   • Can you clearly understand what the code is doing?
   • Are there appropriate comments explaining complex logic or decisions?
2. Coding Standards
   • Is the code aligned with JavaScript/React coding guidelines?
   • No hardcoded values – use constants.
   • No commented-out code.
   • Add meaningful comments (focusing on why, not just what).
   • Avoid deeply nested if/else blocks.
   • Use // TODO: comments for pending tasks.
   • Remove all console.log() statements.
   • Remove unused variables, props, and packages.
3. Naming Conventions
   • Are naming conventions consistent and clear for: Variables , functions , components etc
   • Use const over let (avoid var).
   • Use PascalCase for constants (e.g., MAX_LENGTH_USERNAME).
4. Duplication & Reusability
   • Is any code duplicated or redundant?
   • Should this logic be extracted into a custom hook or reusable component?
   • Can existing components or utilities be reused?
5. Consistency with Codebase
   • Is the code consistent with the project’s existing patterns, styles, and technologies?
6. Code Structure & Responsibilities
   • Is the component or function too large?
   • Does it take more than one responsibility and need to be broken down?
   • Is the logic separated into layers (e.g., Presentation, Business, View)?
7. Non-Functional Requirements 
   • Readability
     • Code should be self-explanatory. If it’s hard to understand, consider refactoring or adding helpful comments.
   • Configurability
     • Values that change frequently should be configurable (not hardcoded).
   • Extensibility
     • Code should allow for easy enhancements with minimal changes.
   • Scalability
     • Ensure the code can handle growing data/usage without performance bottlenecks.
   • Performance
     • Use lazy loading and code splitting where needed.
     • Optimise component performance by using techniques likes React.memo, useMemo, and useCallback.
   • Usability
     • When reviewing UI code:Compare it with the UX design.
     • If the interface seems unclear or inconsistent, get the same clarified with the UX designer.
       
       

Best Practices for Development Teams

• Maintain a standard Checklist for your Team. Regularly review and update team coding guidelines.
• Use tools like ESLint during Local Development, to catch issues early.
• Automate lint checks with pre-commit hooks.
• Integrate SonarQube for continuous Code Quality and Security Analysis.
  
  

Conclusion

Code reviews can sometimes be exhaustive and time-consuming. However, with practice and by following a proper checklist, both the developer and the reviewer can conduct effective code reviews. Approach every code review as an opportunity to learn or improve on something. The checklist above serves as a helpful starting point to become an effective reviewer.