Unload Lifecycle

Unload Lifecycle Overview

Unload Lifecycle lets you structure single-spa work so it stays readable, testable, and easy to scale. Instead of ad-hoc code, you follow a clear pattern that other developers can recognise immediately.

The key is to keep unload lifecycle focused and predictable. Start from the minimal example here, then layer in only the complexity your feature actually needs.

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.

Unload Lifecycle Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to unload lifecycle.

How Unload Lifecycle Works in Single-SPA

Unload 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 Unload Lifecycle

For reliable micro frontends, unload 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

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

Key Takeaways

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