Parcel Lifecycles

Parcel Lifecycles Overview

Parcel Lifecycles 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 parcel lifecycles 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.

Parcel Lifecycles Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to parcel lifecycles.

How Parcel Lifecycles Works in Single-SPA

Parcel Lifecycles 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 Parcel Lifecycles

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

Key Takeaways

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