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We're building tools that help teams migrate from React class components to functional components — starting with free education, moving toward powerful automation. Creator of Unclass, a CLI and analyzer to bring legacy code into the modern React era. I write weekly about React migration, code transformation, and automation with TypeScript.
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🛠️ Purpose: This guide is a foundational deep-dive into React’s internals, crafted for software artisans preparing to migrate class components to modern function components. We’ll walk through React’s core concepts step by step – from the Virtual DO...
🌟 Introduction Welcome back! If you've been following our series, you'll recall that our earlier articles were aimed at architects and managers planning large-scale React migrations. This article marks a shift—now we're diving deeper into the techni...
🌟 Introduction This is the third article from the Unclass team, written with a strong sense of mentorship and care. In our last post, we discussed whether switching from class-based to functional components in React is the right choice. If you're he...
✍️ Introduction Hi there! 👋I'm Daniel, and together with my friend Alberto, we’re the team behind a project called Unclass. We’ve been working in React for years — and we’ve experienced the frustration firsthand:migrating from class components to fu...
Unclass.dev everything that you need to know about how to migrate from react with classes to functions
5 posts
A practical, step-by-step guide to migrating from React class components to functional components.
This is the second article in the React migration series by the Unclass team. In the first article, we introduced the goals of this series and outlined the Unclass project. This time, we're stepping back to ask a more fundamental question: should you even migrate your class components at all?
Functional components with hooks have become the standard in the React ecosystem — but that doesn’t mean every team should jump in. We've gathered recent, engineering-focused insights and best practices to help you make a thoughtful, balanced decision.
Whether you're working with a legacy codebase or just exploring modern best practices, this article offers both sides of the conversation — so you can move forward with clarity and confidence.
👉 You’ll find all the references from our research at the end of this article.
Functional components unlock the full power of React Hooks — like useState, useEffect, and custom hooks — that class components can't natively access. Today, most modern libraries in the React ecosystem offer hook-first APIs, making class components feel increasingly out of sync.
In short, moving to functions aligns your codebase with where React is headed.
Functional components are leaner by default — there's no this, less boilerplate, and fewer built-in assumptions. Some teams have reported up to a 30% reduction in bundle size and faster initial loads after switching to functional patterns.
Hooks like useEffect, useCallback, and useMemo let developers fine-tune performance, avoid unnecessary re-renders, and boost runtime speed — all while keeping the code clean and declarative.
Hooks make it easier to write small, focused components. Instead of duplicating logic across class files, teams can extract and share behavior using custom hooks, supporting DRY and clean code principles.
This shift leads to a clearer separation of concerns and avoids the pain of bloated class components with 500+ lines of lifecycle logic. According to one survey, 75% of engineers say hooks reduce complexity and make code easier to maintain.
📚 Source: MoldStud
Functional components are just plain JavaScript functions — easier to mock, test, and reason about. There’s no this, no constructor bindings, and no awkward lifecycle simulation in tests.
Custom hooks can be tested in isolation, reinforcing a software craftsmanship mindset focused on simplicity, verifiability, and confidence in your codebase.
React’s docs, examples, tools, and third-party libraries are now overwhelmingly focused on functional components with hooks. Core features like concurrent rendering and Server Components are designed with functions in mind.
Migrating helps future-proof your app and ensures you're not working against the grain of where React — and the community — is heading.
Modern React developers often learn hooks first. Many teams report that junior devs or new hires are more comfortable working in functional style and struggle with older class patterns.
By unifying on one style, you reduce mental overhead, simplify onboarding, and make your codebase more approachable. No more wondering why this is undefined or which lifecycle method does what — just clean, functional logic.
The YAGNI principle — “You Aren’t Gonna Need It” — reminds us not to do unnecessary work.
If your class components are well-tested and your app isn’t lacking features that hooks solve, migrating just for trendiness can be wasteful. As one engineer put it:
“If there’s a new feature that benefits from hooks, migrate. Otherwise, why touch it?”
Every migration has cost and risk. Don’t fix what isn’t broken.
Rewriting hundreds of components can introduce regressions and confusion. Especially in mature codebases, mixing styles (half class, half functional) without a clear plan can do more harm than good.
If your system is stable, consider maintaining consistency until there’s a strong need to modernize — or until it can be done incrementally with discipline.
Not every team has time to dedicate to technical refactors. If your roadmap is full of customer-facing features, a migration might feel like a luxury you can’t afford.
In this case, adopt the “Boy Scout Rule”: refactor only the components you touch for new features. Over time, the codebase will modernize itself — without slowing you down today.
If your team is confident with class components but unfamiliar with hooks, a migration may slow you down. React still supports class components, and there's no plan to deprecate them.
Unless your team is ready to adopt the functional style fully, forcing a switch can introduce more bugs and confusion than it resolves.
Some features — like Error Boundaries — still require class components (as of 2025). You may also rely on third-party libraries that assume class patterns.
In these rare cases, mixed paradigms are fine. Just verify that critical functionality or tooling won’t break before migrating.
React has clearly moved toward functional components, but your team’s migration decision should be based on value — not fashion.
✅ Migrate when it helps you:
Leverage hooks
Improve maintainability
Reduce technical debt
Align with modern tooling and hiring
❌ Delay migration when:
Your app is stable and well-tested
You lack time, budget, or need
The risk outweighs the benefit
Craftsmanship means respecting context and solving real problems. Migrate when it makes your system more sustainable, testable, and productive — not because Twitter said so.
As always — write less code, make it better.
Ihnatovich, Dzmitry. From Class Components to Hooks: A Migration Strategy. Medium, 2025.
Ifeanyi Emmanuel. Choosing Between Class and Functional Components in React. Stackademic, 2023.
MoldStud (Cătălina Mărcuță et al.). Migrating from Class Components to Hooks – Effective State Management in React for MERN Apps. 2025.
Glinteco. Why You Should Use Functional Components & Hooks in ReactJS. 2023.
Reddit r/reactjs: “Is it a good decision to convert class-based components to functional components?” 2021.
Stack Overflow: “Should we change class component to functional component?” Answer by rockTheWorld. 2020.
Sean LaFlam. Is There Any Reason to Still Use React Class Components? Medium, 2021.
Reddit r/reactnative: “Is it worth converting class-based components to functional components?” 2021.
GeeksforGeeks. What is YAGNI principle (You Aren’t Gonna Need It)? 2024