Shared Component Library

Shared Component Library Overview

Shared Component Library is a building block you will reach for often in single-spa. It keeps related logic together and makes your intent obvious to reviewers and future maintainers.

When you learn shared component library properly, you avoid the guesswork that leads to bugs and rework. The example below shows the shape you will use in most real single-spa projects.

// shared utility module exposed via the import map
export const authService = {
  getToken: () => localStorage.getItem('token'),
};

// consumed by any micro frontend
import { authService } from '@org/utils';

Shared utility modules provide cross-app services like auth without tight coupling.

Shared Component Library Example

registerApplication({
  name: '@org/app',
  app: () => System.import('@org/app'),
  activeWhen: ['/app'],
});
start();

• Start from a minimal Shared Component Library example and grow it only as needed.
• Keep configuration explicit so Shared Component Library behaves the same in every environment.
• Name things clearly so teammates understand your Shared Component Library at a glance.
• Add tests around Shared Component Library early to lock in expected behaviour.

Single-SPA Cheatsheet

Core single-spa APIs related to shared component library.

How Shared Component Library Works in Single-SPA

Shared Component Library is part of how single-spa lets multiple applications — even in different frameworks — coexist on one page. A root config registers each app and controls when it is active.

Shared utility modules provide cross-app services like auth without tight coupling.

• A root config registers apps and calls start().
• Each app exports bootstrap, mount, and unmount lifecycles.
• activeWhen decides which routes each app owns.
• Import maps resolve each app's bundle at runtime.

Practical Guidance for Shared Component Library

For reliable micro frontends, shared component library should isolate failures and keep shared state minimal. Let each team own its app end to end while agreeing on a few shared contracts.

Common Mistakes

• Skipping error handling and edge cases when wiring up shared component library.
• Leaving shared component library untested, so regressions slip into production.
• Over-engineering shared component library before you actually need the extra flexibility.
• Ignoring documentation, which makes shared component library hard for the next developer to change.

Key Takeaways

• Shared Component Library is a core part of working effectively with single-spa.
• Start small and keep shared component library focused on a single responsibility.
• Apply consistent patterns so shared component library scales across your project.
• Test and document shared component library to keep it maintainable over time.