React Code Review:
Checklist, Key Challenges, and Best Practices

Issues slip through reviews when you focus on just the surface level. A strong React code review process allows you to focus on the most important parts of the codebase.

This guide explains what a code review should actually cover, how to assess your codebase, and which common mistakes slow teams down. More importantly, we include a practical React TypeScript code review checklist to align reviewers and standardize expectations.

React (also known as React.js and ReactJS) is an open-source JavaScript library with reusable components. A codebase built on this library can grow fast with component trees, hooks, and functions. Small errors during development are inevitable.

A comprehensive React code review can help you:

• Improve code quality: Reviewers identify and fix logic mistakes, incorrect state updates, broken edge states, and excessive functions that cause instability.
• Avoid technical debt: With regular code reviews, a React codebase will avoid compounding issues that make it harder to understand, change, and test.
• Codebase consistency: Regular assessments enforce the same naming, folder structure, and other style conventions that keep the codebase understandable.
• Better maintainability: Reviews also help make the components smaller and more isolated, making the React codebase easier to manage as it grows.
• Early security awareness: Security reviews highlight risky data handling, unsafe inputs, and weak permission checks before they lead to major incidents.
• Easier domain knowledge sharing: Review results allow you to spread key requirements and practical solutions that help avoid repeating the same mistakes.

To conduct a review correctly, you should understand what you’re looking for and how to do it.

A review works best when it focuses on a few core qualities. It’s really up to you what to assess, but we suggest breaking it into components and then prioritizing according to your needs.

Readability

Readability means your developers, including those who didn’t write the original code, can understand the logic. In React, you should make responsibilities easy to infer and ensure the behavior does not hide behind structure. Look for places where the reader must analyze too many details at once, and flag them for optimization or commenting.

Updateability

Updateability measures how safely the code can change. Code analysis should focus on whether changes remain local, predictable, and manageable to extend. You have to scan for tight coupling that makes updates impact other, seemingly unrelated, functions.

Reusability

Reusability means cutting repeated work without burning the codebase in abstractions. The React code review checklist should identify copy-pasted chunks of code that may complicate maintenance.

Performance

A performance review focuses on whether features remain responsive as demand increases. Reviews should catch excessive functions and other design decisions that consume a disproportionate amount of resources.

Scalability

Scalability shows how well the code holds up as the React applications grow. During a review, your team should determine if the code is easy enough to search through, modify, and expand with new features.

Cybersecurity

A security review verifies whether the frontend leaks sensitive details through interactions or if it bypasses rules by assumption. The reviewer verifies what the UI should trust, what it should never trust, and what it must handle cautiously.

These components define what matters during a review, which you can use to create a repeatable reference.

Our checklist is built to make your review easier, faster, and more all-encompassing. We divided it into parts.

Syntax and formatting

Clean syntax makes the React codebase easier to review. It helps you get rid of the noise, so reviewers can focus on data flows, logic, and core UI behavior.

Here are the rules your React codebase should follow:

• Keep unified naming for components, functions, variables, and files across the project.
• Use clear prefixes for booleans (such as is, has, can, or should) so conditions read as plain statements.
• Make function and component names descriptive of the action or result.
• Prefer const by default and let only if you require reassignment.
• Use early return checks and helper functions instead of deeply nested conditionals.
• Remove console.log statements, unreachable branches, and temporary debugging code.
• Use named constants and shared configuration instead of hardcoded numbers or strings.
• Delete unused imports, variables, props, and packages to reduce clutter and misleading signals.

Codebase consistency

Consistency makes the React app easier to update. Developers will spend less time on guesswork when upgrading your app.

• Follow a single style, folder structure, data fetching approach, and module boundaries.
• Avoid parallel solutions and duplicate libraries that do the same job (like two date libraries).
• Stick to one TypeScript style defined by the codebase rules.
• Reuse React hooks, shared components, and utilities instead of duplicating logic.
• Align imports with the project’s rules for file types, paths, and aliases, so relationships remain predictable for developers.
• Store all user-facing text in the translation system instead of hardcoding strings to keep UI content consistent.

Component design

React component code review helps verify that state, effects, and rendering logic are correct in pull requests and behave predictably when executed in the browser.

• Prefer functional components by default unless there is a clear technical reason to use class components.
• Check basic accessibility support (such as keyboard navigation and screen reader compatibility).
• Keep props small and single purpose instead of passing large data objects through multiple layers.
• Store state only for values that change due to user actions or asynchronous updates.
• Verify that useEffect dependencies reflect only the values that should trigger the effect.
• Ensure side effects run inside effect hooks or event handlers and never during render.
• Utilize stable keys when rendering lists so React can correctly track items when their order changes.
• Use context or composition to avoid long, hard-to-maintain prop chains.

Code structure and responsibilities

Reviewers should make sure components are modular enough to test and update without breaking unrelated app functionality.

• Make sure each component has one job, splitting oversized files and functions when necessary.
• Separate the UI, rules, and data access responsibilities per component.
• Avoid inline expressions that obscure the UI’s structure by isolating event handlers and data transforms.
• Ensure configurations are centralized for routes, endpoints, and feature flags.
• Extract repeated logic into custom React hooks and helpers if the same decision flow appears in multiple places.
• Confirm that shared components don’t change behavior during editing.

TypeScript accuracy

React TypeScript code review helps prevent invalid setups. However, your team should be extra careful to ensure it correctly describes the data and protects component contracts.

• Check that the codebase uses the any type only when necessary, because it disables type safety and allows errors to pass.
• Ensure API types reflect real backend responses, including missing fields and optional values, so the UI doesn’t rely on nonexistent data.
• Type props and return values for shared components and unclear interfaces to make expectations explicit.
• Include null and undefined in types when those values can occur.
• Remove unused types and narrow overly broad ones instead of widening them to satisfy the TypeScript compiler.

Performance optimization

The reviewers should look for obvious performance issues that slow down the entire app. It’s more about dealing with obvious problems than optimizing the code quality across the codebase.

• Move expensive calculations and transforms outside of render, so they don’t repeat on every input.
• Search parent components for recreated logic and functions that trigger child rerenders on updates.
• Apply memoization (React.memo, useMemo, and useCallback) only on specific occasions, like when you need to remove real rerenders.
• Confirm that async code does not trigger duplicate requests or apply stale results.
• Use lazy loading and code splitting for heavy pages or rarely used modules.
• Make sure long lists do not render the entire dataset at once.
• Check async flows for duplicated fetches and stale updates.

Error handling

The React code review process should include checking how the app behaves when things go wrong. You are confirming that errors lead to clear outcomes instead of silent breaks or frozen screens.

• Check if the app treats null (missing) or undefined (partial) data as input, so the UI never assumes this data exists.
• Ensure API failures show a clear fallback state.
• Make sure errors surface consistently in a predictable way.
• Use try-and-catch around code that can fail, especially parsing, storage access, and risky data changes.
• Prevent async code from updating state after a component unmounts to avoid unnecessary warnings.
• Verify error boundaries for complex sections to avoid crashing the entire app.

Test coverage

Relevant and comprehensive test scenarios in the PR help prevent issues during development and reduce the reviewer’s work later on.

• Make sure unit tests cover logic for business-critical processes and other tasks that affect users.
• Add integration tests if multiple parts work together through state, routing, or data.
• Check if component tests cover important UI states, like loading, empty, error, and success.
• Ensure tests include edge cases (such as missing fields, partial responses, or unusual values).
• Inquire how often the team updates tests, preferably fixing outdated scenarios instead of removing them.
• Verify E2E tests cover critical flows (like authorization and payment) when the PR touches them.

Risks and vulnerabilities

The React code review should check if the frontend code follows safety rules, even during edge cases and tampering.

• Make sure there are procedures that validate user input before sending it to the UI logic or APIs.
• Check if the rules match product requirements so malicious inputs never slip through.
• Configure the system to treat all raw HTML rendering as a high-risk action that requires clear justification.
• Confirm that authorization happens on the server instead of the client side.
• Review new dependencies to confirm they are necessary and don’t introduce risks.
• Verify that logs and debugging views don’t reveal internal or personally identifiable information.
• Avoid persisting sensitive data and tokens in exposed locations unless there’s a logical and documented reason.

Documentation and comments

A properly documented codebase with descriptive comments helps you review the React code faster and avoid expensive guesswork.

• Make sure comments explain the reasons behind decisions rather than obvious details about the code.
• Check if documentation captures compromises, constraints, and edge cases.
• Verify that public component APIs are clearly documented, explaining what each prop controls.
• Assess how often the team updates the README file and feature notes.
• Ensure TODO comments describe concrete follow-ups, explaining the importance of each change.

A checklist helps reviewers, but they might still need habits to make the assessment more efficient.

You should aim to make a React code audit or review as predictable as possible. The following habits and strategies can help your team identify, fix, and prevent issues.

1. Define review goals and scope: Reviewers should understand the prioritized review areas and focus, so they don’t waste time debating style and unrelated edge cases.
2. Introduce code quality metrics: You need quantifiable metrics to judge objectively whether the review actually improved the React codebase.
3. Require a clear PR description: Explain what changed and what was left out, so different review teams can more easily understand verified decisions.
4. Attach proof of UI changes: Screenshot or record critical changes in layout, states, and interaction to help QA specialists validate the code without running it.
5. Ensure branch and commit readiness: Align the branch with the latest main code and group commits logically to make the changes easier to follow.
6. Run static analysis in commits: Automated linting tools and static rule checkers should catch basic issues early.
7. Confirm environment configuration changes: Double-check changes in feature flags, environment variables, and configuration, because they can break seemingly correct code.
8. Give actionable and categorized feedback: Tell developers exactly what they should fix and categorize feedback by priority.
9. Maintain a professional tone: Comments should address problems in the code and remain respectful to the team.

Even well-structured reviews don’t save you from mistakes that appear far more frequently than you might imagine.

Even a good React code review checklist, best practices, and tools aren’t a guarantee. You should be aware of the following problems as you prepare to assess your codebase.

Oftentimes, you just need experience in your first couple of code audits or reviews. And that’s easier with an outside perspective.

A code review tests all aspects of your app and leaves you with a better understanding of it. It helps you catch weak assumptions, unclear intent, and design choices that raise risks.

Without expertise, it’s still easy to spread your efforts thin and get caught up in minor mistakes. An experienced team can assess your source code and share practical insight that will improve your review.

Contact us if you need a second set of eyes or a full audit.