Modular Architecture in Frontend: How to Structure a Project

Modular architecture is approach where project is divided into autonomous blocks (modules), each having clear area of responsibility and minimal connections with others. This facilitates maintenance, testing and application scaling, and helps teams effectively divide tasks.

Key Idea:

Modules don't directly depend on each other — they can only use "core" to interact with common services and UI components.
Any module implementation details (internal files, functions, states) are encapsulated and accessible from outside only through Public API.

Main Principles

Module Independence

Changes in one module don't break work of other modules. If module functionality is no longer needed, it's enough to delete its folder, and system continues working without that part of functionality.

Encapsulation

Everything related to module (components, styles, utilities, logic) is stored inside one folder. Interacting with module from outside is possible only through Public API, which protects internal implementation from external dependencies.

Dependency Only on "Core"

If modules need common services (e.g., logger, network requests, routing), they take them from core. Modules shouldn't directly depend on each other.

Unidirectional Flow

Data flows top to bottom: pages ⇒ modules ⇒ components ⇒ UI.
Such structure simplifies understanding where business logic is processed.

Structure Example

Pros

Scalability: adding new module or removing old one doesn't break entire application.
Clear boundaries: clearly understood what functionality is responsible for what and where to find it.
Isolation: internal implementation is hidden from other parts of application.
Simple team work: each developer can work on their module without affecting others.

Cons

Division complexity: not always obvious when to extract code into separate module, and when to leave in components.
Potential duplication: if one module can't directly use another, sometimes you have to copy part of code or extract common functionality to core/shared.
Implicit connections: global data (e.g., store) can be used differently, creating indirect dependencies.

Summary:

Modular architecture is well suited for medium and large projects where clear separation of responsibility areas and minimization of internal connections between functions is necessary. At same time it's important to properly organize core — it's where common services and components accessible to all modules are stored.