systemjs

What is systemjs?

SystemJS is a dynamic module loader that can load ES modules, AMD, CommonJS, and global scripts in the browser and Node.js. It provides a way to load modules asynchronously and supports various module formats, making it a versatile tool for managing dependencies and module loading in JavaScript applications.

What are systemjs's main functionalities?

Loading ES Modules

SystemJS can dynamically import ES modules. The code sample demonstrates how to load an ES module asynchronously and handle the loaded module.

System.import('/path/to/module.js').then(function(module) {
  console.log(module);
});

Loading CommonJS Modules

SystemJS can also load CommonJS modules. The code sample shows how to load a CommonJS module asynchronously.

System.import('/path/to/commonjs-module.js').then(function(module) {
  console.log(module);
});

Loading AMD Modules

SystemJS supports loading AMD modules. The code sample demonstrates how to load an AMD module asynchronously.

System.import('/path/to/amd-module.js').then(function(module) {
  console.log(module);
});

Loading Global Scripts

SystemJS can load global scripts that do not export any modules. The code sample shows how to load a global script asynchronously.

System.import('/path/to/global-script.js').then(function() {
  console.log('Global script loaded');
});

Configuring SystemJS

SystemJS allows configuration for module loading. The code sample demonstrates how to configure the base URL, paths, and module mappings.

System.config({
  baseURL: '/base/url',
  paths: {
    'npm:': 'https://unpkg.com/'
  },
  map: {
    'jquery': 'npm:jquery@3.5.1/dist/jquery.js'
  }
});

Other packages similar to systemjs

requirejs

RequireJS is a JavaScript file and module loader. It is optimized for in-browser use, but it can be used in other JavaScript environments, such as Rhino and Node. Compared to SystemJS, RequireJS primarily focuses on AMD modules and does not support as many module formats.

webpack

Webpack is a module bundler that takes modules with dependencies and generates static assets representing those modules. Unlike SystemJS, which is a dynamic module loader, Webpack bundles modules at build time, which can result in better performance for production applications.

browserify

Browserify allows you to use Node.js-style require() to organize your browser code and load modules. It transforms Node.js modules into a format that can be used in the browser. Compared to SystemJS, Browserify focuses on CommonJS modules and does not support as many module formats.

es-module-loader

ES Module Loader is a polyfill for the ES Module Loader specification. It provides a way to load ES modules in environments that do not natively support them. Compared to SystemJS, ES Module Loader is more focused on ES modules and does not support other module formats.

README

SystemJS

Configurable module loader enabling dynamic ES module workflows in browsers and NodeJS.

SystemJS 0.20 release notes

SystemJS is currently sponsored by Canopy Tax.

• Loads any module format when running the ~15KB development build.
• Loads ES modules compiled into the System.register module format for production with exact circular reference and binding support
• Supports RequireJS-style map, paths, and bundles configuration.

Built with the ES Module Loader project, which is based on principles and APIs from the WhatWG Loader specification, modules in HTML and NodeJS.

Supports IE9+ provided a promises polyfill is available in the environment.

For discussion, join the Gitter Room.

Documentation

• Getting Started
• Module Formats
• Production Workflows
• Configuration API
• System API
• Plugins
• Creating Plugins
• Production Build and Resolution

Basic Use

Browser Development

<script src="systemjs/dist/system.js"></script>
<script>
  SystemJS.import('/js/main.js');
</script>

The above will support loading all module formats.

To load ES6 code with in-browser transpilation, one of the following transpiler plugins must be configured:

• Babel
• TypeScript
• Traceur

Browser Production

When all modules are already transpiled into the System.register module format (which can be output via Babel or TypeScript through any build workflow), a production-only loader can be used:

<script src="systemjs/dist/system-production.js"></script>
<script>
  SystemJS.import('/js/main.js');
</script>

Configuration support in the production loader includes baseURL, paths, map, contextual map, bundles and depCache.

NodeJS

To load modules in NodeJS, install SystemJS with:

  npm install systemjs

If transpiling ES modules, install the transpiler plugin following the instructions from the transpiler project page.

We can then load modules equivalently in NodeJS as we do in the browser:

var SystemJS = require('systemjs');

// loads './app.js' from the current directory
SystemJS.import('./app.js').then(function (m) {
  console.log(m);
});

To import a module with the NodeJS module resolution, import with import moduleName from '@node/module-name'.

Running the tests

  npm run build && npm run test

License

MIT