Mount Lifecycle

Mount Lifecycle Overview

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

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.

Mount Lifecycle Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to mount lifecycle.

How Mount Lifecycle Works in Single-SPA

Mount 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 Mount Lifecycle

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

Key Takeaways

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