Single-SPA Do's and Don'ts

Do's and Don'ts is an important part of building production-ready single-spa systems. This lesson explains what do's and don'ts means, how it works, and how to apply it with practical examples you can reuse.

Do's and Don'ts Overview

Do's and Don'ts 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 do's and don'ts 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.

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.

Do's and Don'ts Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to do's and don'ts.

API	Example	Purpose
registerApplication	`registerApplication({ name, app, activeWhen })`	Register a micro frontend
activeWhen	`activeWhen: ['/checkout']`	Route ownership
start	`start()`	Begin routing
bootstrap	`export async function bootstrap()`	One-time setup
mount	`export async function mount(props)`	Render the app
unmount	`export async function unmount(props)`	Clean up the app
import map	`systemjs-importmap`	Locate app bundles

How Do's and Don'ts Works in Single-SPA

Do's and Don'ts 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 Do's and Don'ts

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

Concern	Recommendation
Isolation	One app's crash should not break others
Shared state	Prefer shared utility modules over globals
Routing	Keep activeWhen rules explicit and non-overlapping
Deployment	Release via import-map updates per app

Common Mistakes

Copying do's and don'ts snippets without understanding what each line does.
Skipping error handling and edge cases when wiring up do's and don'ts.
Leaving do's and don'ts untested, so regressions slip into production.
Over-engineering do's and don'ts before you actually need the extra flexibility.

Key Takeaways

Do's and Don'ts is a core part of working effectively with single-spa.
Start small and keep do's and don'ts focused on a single responsibility.
Apply consistent patterns so do's and don'ts scales across your project.
Test and document do's and don'ts to keep it maintainable over time.

Pro Tip

Pair do's and don'ts with automated tests from day one. It is far cheaper to catch single-spa regressions in CI than in production.