SystemJS Output

SystemJS Output Overview

SystemJS Output 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 systemjs output focused and predictable. Start from the minimal example here, then layer in only the complexity your feature actually needs.

<script type="systemjs-importmap">
{
  "imports": {
    "@org/root-config": "//localhost:9000/org-root-config.js",
    "@org/navbar": "//localhost:8500/org-navbar.js"
  }
}
</script>

Import maps tell SystemJS where to load each micro frontend bundle at runtime.

SystemJS Output Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to systemjs output.

How SystemJS Output Works in Single-SPA

SystemJS Output 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.

Import maps tell SystemJS where to load each micro frontend bundle at runtime.

• 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 SystemJS Output

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

Key Takeaways

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