single-spa-react

In this lesson you will learn single-spa-react in single-spa, why it matters within react integration, and how to use it correctly with clear, copy-ready examples.

single-spa-react Overview

At its core, single-spa-react 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 single-spa-react pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

import React from 'react';
import ReactDOMClient from 'react-dom/client';
import singleSpaReact from 'single-spa-react';
import Root from './root.component';

const lifecycles = singleSpaReact({
  React,
  ReactDOMClient,
  rootComponent: Root,
});

export const { bootstrap, mount, unmount } = lifecycles;

single-spa-react adapts a React app into single-spa lifecycle functions.

single-spa-react Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to single-spa-react.

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 single-spa-react Works in Single-SPA

single-spa-react 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-react adapts a React app into single-spa lifecycle functions.

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 single-spa-react

For reliable micro frontends, single-spa-react 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 single-spa-react snippets without understanding what each line does.
Skipping error handling and edge cases when wiring up single-spa-react.
Leaving single-spa-react untested, so regressions slip into production.
Over-engineering single-spa-react before you actually need the extra flexibility.

Key Takeaways

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

Pro Tip

Bookmark this single-spa-react pattern and reuse it. Consistency across your single-spa codebase is worth more than clever one-off solutions.