Unmount Lifecycle

Unmount Lifecycle Overview

Unmount Lifecycle 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 unmount lifecycle 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.

export async function bootstrap(props) {
  // one-time setup
}

export async function mount(props) {
  // render the app into props.domElement
}

export async function unmount(props) {
  // tear down and clean up
}

Every single-spa application exports bootstrap, mount, and unmount lifecycle functions.

Unmount Lifecycle Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to unmount lifecycle.

How Unmount Lifecycle Works in Single-SPA

Unmount Lifecycle 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.

Every single-spa application exports bootstrap, mount, and unmount 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 Unmount Lifecycle

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

Key Takeaways

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