single-spa

What is single-spa?

single-spa is a JavaScript framework for front-end microservices. It allows you to build and manage multiple microfrontends that can coexist and interoperate within a single web application. This enables teams to work independently on different parts of a web application, using different frameworks if necessary.

What are single-spa's main functionalities?

Registering Applications

This feature allows you to register multiple applications with single-spa. Each application can be loaded dynamically and activated based on the URL path.

const singleSpa = require('single-spa');
singleSpa.registerApplication({
  name: 'app1',
  app: () => System.import('app1'),
  activeWhen: ['/app1'],
  customProps: {}
});
singleSpa.start();

Mounting and Unmounting Applications

This feature allows you to manually mount and unmount applications, giving you fine-grained control over which applications are active at any given time.

const singleSpa = require('single-spa');
singleSpa.registerApplication({
  name: 'app2',
  app: () => System.import('app2'),
  activeWhen: ['/app2'],
  customProps: {}
});
singleSpa.start();

// Manually mount an application
singleSpa.mountRootParcel('app2', { domElement: document.getElementById('app2-container') });

// Manually unmount an application
singleSpa.unmountRootParcel('app2');

Custom Events

This feature allows you to dispatch and listen for custom events, enabling communication between different microfrontends.

const singleSpa = require('single-spa');
singleSpa.registerApplication({
  name: 'app3',
  app: () => System.import('app3'),
  activeWhen: ['/app3'],
  customProps: {}
});
singleSpa.start();

// Dispatch a custom event
window.dispatchEvent(new CustomEvent('custom-event', { detail: { someData: 'data' } }));

// Listen for a custom event
window.addEventListener('custom-event', (event) => {
  console.log(event.detail.someData);
});

Other packages similar to single-spa

qiankun

qiankun is a micro-frontend framework based on single-spa. It provides additional features like sandboxing and lifecycle hooks, making it easier to manage microfrontends in complex applications.

mooa

mooa is a micro-frontend framework inspired by single-spa. It focuses on Angular applications and provides a simpler API for integrating multiple Angular microfrontends.

icestark

icestark is a micro-frontend framework developed by Alibaba. It offers a set of tools and conventions for building and managing microfrontends, with a focus on React and Vue applications.

README

single-spa

Combine multiple SPAs into one SPA by implementing lifecycle functions. This allows you to:

• Use multiple frameworks on the same page without refreshing the page (React, Angular 1, Angular 2, Ember, or whatever you're using)
• Write code using a new framework, without rewriting your existing app
• Lazy load code for improved initial load time.

Demo and examples

A live demo is available and the source code for that demo is available in the single-spa-examples repository.

Architectural Overview

Single-spa takes inspiration from React component lifecycles by applying lifecycles to entire applications. It started out of a desire to use React + react-router instead of being forever stuck with our Angular 1 + ui-router application, but now single-spa supports almost any framework coexisting with any other. Since Javascript is notorious for the short-life of its many frameworks, we decided to make it easy to use whichever frameworks you want.

Apps built with single-spa are made up of the following pieces:

1. Many child applications, each of which can be a distinct SPA. Child applications respond to url routing events and must know how to bootstrap, mount, and unmount themselves from the DOM. For example, your React or Angular applications are child applications which are either active or dormant. When active, they listen to url routing events and put content on the DOM. When dormant, they do not listen to url routing events and are totally removed from the DOM.
2. A root application where child applications are registered. Each child application is registered with three things:
3. A name
4. A function to load the child application's code
5. A function that determines when the child application is active/dormant.

How hard will it be to use single-spa?

single-spa works with es5, es6+, typescript, webpack, systemjs, gulp, grunt, bower, or really anything build system you can think of. You can npm install it, jspm install it, or even just use a <script> tag if you prefer. If you're not starting your application from scratch, you'll have to migrate your SPA to become a single-spa child application.

single-spa works in Chrome, Firefox, Safari, IE11, and Edge.

Isn't single-spa sort of a redundant name?

Yep

Documentation

See the docs. If you're looking for help with specific frameworks or build systems (React, Angular, Webpack, etc), check out the ecosystem wiki

Simple Usage

Note: this example uses jspm, but check out the ecosystem documentation to see how to set everything up with webpack or other build systems.

npm install -g jspm@beta
jspm init
jspm install npm:single-spa

Create an index.html file (see docs for more detail).

<html>
  <head>
    <script src="jspm_packages/system.src.js"></script>
    <script src="jspm.browser.js"></script>
    <script src="jspm.config.js"></script>
    <script>
      System.import('src/main.js');
    </script>
  </head>
  <body>
    <div id="main-content"></div>
  </body>
</html>

Create the root application (see docs for more detail).

// src/main.js
import { declareChildApplication, start } from "single-spa";
declareChildApplication('app1', () => System.import('/apps/app1.js'), () => window.location.hash === '');
start()

Create the child application (see docs for more detail).

document.getElementById('main-content').textContent += "App1 is loaded.";

// apps/app1.js
export function bootstrap() {
  return new Promise((resolve, reject) => {
    document.getElementById('main-content').textContent += "App1 is bootstrapped.";
    resolve();
  });
}

export function mount() {
  return new Promise((resolve, reject) => {
    document.getElementById('main-content').textContent += "App1 is mounted!";
    resolve();
  });
}

export function unmount() {
  return new Promise((resolve, reject) => {
    document.getElementById('main-content').textContent = "";
    resolve();
  });
}

API

See single-spa api and child application api.