How SOLID Is Your Frontend App: Writing Clean and Scalable Code

♻️ Knowledge seeks community 🫶 #10

Hey,

Hope you are doing well!

I just wanted to say a big thank you for being here! We’re growing little by little, and having you receive this email truly means a lot to me. You’re awesome! 😊

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Recently, I've been concentrating on understanding various approaches to writing clean and maintainable code, as well as the underlying reasoning behind these practices.

While I'm already committed to this focus, what prompted me to write this article is the realization that much of our coding style is often supported by theories that frequently go unnoticed. And later on, during technical discussions, we often struggle to explain why we wrote the code in a particular way.

An example related to this situation is building on top of the SOLID principles without even noticing the theory behind our solution.

What are these SOLID Principles?

SOLID principles, introduced by Robert C. Martin, are a set of guidelines aimed at improving software design. While commonly discussed in backend contexts, these principles are equally valuable in frontend development—especially for building scalable, maintainable, and testable UI applications.

Next we are going to explore together how each of the SOLID principles is getting implemented in frontend development.

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SOLID Principles in Frontend

Single Responsibility Principle (SRP)

• Definition: A component should have one reason to change.

• Frontend Context: In the frontend, the SRP encourages us to design components, functions, and modules where each has a focused purpose. A component should ideally be responsible for one specific aspect of the UI or a single piece of application logic.

• Strategy:

  • Split a large component handling multiple responsibilities (data fetching, state updates, rendering) into smaller, focused components.

  • For example: Separate a UserProfile component into UserProfileData (data fetching) and UserProfileView (rendering).

    

• Benefits: Components become more reusable and easier to test. Collaboration improves as responsibilities are clearly split.

Open/Closed Principle (OCP)

• Definition: Software entities should be open for extension but closed for modification.

• Frontend Context: In the frontend, the OCP encourages us to design components and modules that can adapt to new requirements without requiring changes to their existing code. This promotes stability and reduces the risk of introducing regressions when adding new features or variations. We achieve this by creating abstractions that allow us to extend behavior through inheritance (though less common in modern frontend frameworks), composition, configuration, or by emitting events that other parts of the application can react to.

• Strategy:

  • Use props and composition to extend behavior without modifying existing components.

  • For example: Create a Button component that accepts a renderIcon prop for adding icons without modifying the base component.

    

• Benefits: Stable base components with customizable behavior encourage reuse and reduce regression risk.

Liskov Substitution Principle (LSP)

• Definition: Objects of a superclass should be replaceable with objects of a subclass without breaking the application.

• Frontend Context: In the frontend, the LSP becomes particularly relevant when dealing with component inheritance or when designing higher-order components (HOCs) or render props. It emphasizes that specialized components should maintain the core contract and expected behavior of their more general counterparts. If a derived component behaves in unexpected ways when used in place of its base component, it violates the LSP and can lead to unpredictable bugs.

• Strategy:

  • Use polymorphism and component inheritance (or composition) to extend behavior.

  • For example: A BaseModal component that can be extended into ConfirmationModal or InfoModal.

    

• Benefits: Predictable and consistent behavior with interchangeable components.

Interface Segregation Principle (ISP)

• Definition: Clients should not be forced to depend on interfaces they do not use.

• Frontend Context: In frontend development, the ISP often manifests in how we design component props, module APIs, and especially when dealing with more abstract concepts like data providers or service integrations. When a component or module has a large interface with many optional or conditional properties/methods, it can become harder to understand, use, and maintain. Clients might end up depending on parts of the interface they don't actually need, leading to unnecessary coupling and potential issues if those unused parts change.

• Strategy:

  • Create multiple smaller interfaces rather than a single large one.

  • For example: ButtonProps and LinkProps instead of a large ComponentProps.

    

• Benefits: Easier to understand, test, and reuse smaller components with specific APIs.

Dependency Inversion Principle (DIP)

• Definition: Depend on abstractions, not concretions.

• Frontend Context: In frontend development, the DIP is crucial for decoupling our UI components (high-level modules) from specific implementations of data fetching, state management, or external services (low-level modules). By introducing abstractions (like interfaces, abstract classes, or even just well-defined function signatures), we can make our components more independent, easier to test with mock implementations, and less susceptible to changes in the underlying infrastructure.

• Strategy:

  • Use dependency injection for services and state management.

  • For example: Inject API service into a context or Zustand store instead of hardcoding it inside a component.

    

• Benefits: Easy to swap services or mock dependencies during testing.

Final Thoughts

Chances are, you’re already applying many of the SOLID principles in your frontend code without even realizing it. Whether you split your UI components by responsibility, rely on composition for flexibility, or decouple services through abstraction—these practices are all rooted in SOLID thinking.

What’s most important is to understand the why behind these principles. When you do, you’ll find it easier to explain your technical decisions, reason about your architecture, and make intentional improvements.

Hopefully, the examples in this article helped you connect the dots between theory and practice. Because in the end, SOLID isn’t about rigid rules—it’s about writing thoughtful, sustainable code that scales with your team and your users.

Until next time 👋,

Stefania

P.S. Don’t forget to like, comment, and share with others if you found this helpful!

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Articles from the ♻️ Knowledge seeks community 🫶 collection:

https://stefsdevnotes.substack.com/t/knowledgeseekscommunity

Articles from the ✨ Frontend Shorts collection:

https://stefsdevnotes.substack.com/t/frontendshorts

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👋 Get in touch

Feel free to reach out to me here on Substack or on LinkedIn.