Utility Modules

Utility Modules Overview

At its core, utility modules is about doing one thing well inside your single-spa project. Once you understand the pattern, you can apply it consistently across features and teams.

Good utility modules pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

import { registerApplication, start } from 'single-spa';

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

start();

single-spa orchestrates multiple framework apps on one page through a root config.

Utility Modules Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to utility modules.

How Utility Modules Works in Single-SPA

Utility Modules 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.

single-spa orchestrates multiple framework apps on one page through a root config.

• 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 Utility Modules

For reliable micro frontends, utility modules 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 utility modules.
• Leaving utility modules untested, so regressions slip into production.
• Over-engineering utility modules before you actually need the extra flexibility.
• Ignoring documentation, which makes utility modules hard for the next developer to change.

Key Takeaways

• Utility Modules is a core part of working effectively with single-spa.
• Start small and keep utility modules focused on a single responsibility.
• Apply consistent patterns so utility modules scales across your project.
• Test and document utility modules to keep it maintainable over time.