Bare AMD Loader ·

Simple Asynchronous Module Definition loader dedicated to bare module specifier support.

It tries to be the smallest AMD loader that:

• uses a Promise-based API
• supports parallel module loading
• avoids unnecessary requests by caching module definitions in memory, both for concurrent and future calls
• only resolves paths that map a bare import to url (like axios: https://unpkg.com/axios/dist/axios.js)
• allows one to inject a local module as a dependency
• only sets AMD's define in the global namespace

See Motivation if you still don't know whether bare-amd-loader is for you!

Usage

Installation

The most common way to install is via npm:

npm i -D bare-amd-loader

API

The whole API revolves around the single named export load function.

function load(modules: string | string[], config: Config): Promise<any>;

It can be used to load a single module:

load("axios", config).then(axios => {
  // use axios
});

Or load multiple modules at once:

load(["react", "react-dom", "react-router"], config).then(
  ([React, ReactDOM, ReactRouter]) => {
    // use em'
  }
);

The config object allows one to specify how bare module specifiers like react get resolved.

type Config = {
  paths: {
    [moduleId: string]: string;
  };
  modules?: {
    [moduleId: string]: any;
  };
};

One can map them via either:

• config.paths: Object that maps a module name to a url. You will at least need to map here the main module(s) to load.
• config.module: Optional object that maps a module name to a module reference. Useful for injecting dependencies that are already within scope.

Example

In this example we are loading an AMD compatible widget asynchronously (myWidget), from within a bundled application, that depends:

• On specific React and ReactDOM versions from a CDN
• On the bundled version of lodash

import { load } from "bare-amd-loader";
import _ from "lodash";

const config = {
  paths: {
    myWidget: "url-to-myWidget.js",
    react: "https://unpkg.com/react@16.8.3/umd/react.production.min.js",
    "react-dom":
      "https://unpkg.com/react-dom@16.8.3/umd/react-dom.production.min.js",
  },
  modules: {
    lodash: _,
  },
};

load("myWidget", config).then(myWidget => {
  // myWidget is ready to be used
});

Motivation

Extendable Apps

Even in the current world of bundled web applications, there are particular scenarios where one needs to load some app extensions (complex widgets / micro-frontends) that follow certain requirements:

• are isolated from each other
• can be loaded asynchronously
• depend on specific libraries' versions

ES Modules vs AMD

Ideally, we would all be relying on ES modules for authoring everything, given that:

• they are native to modern browsers
• support synchronous and asynchronous dependency loading
• together with the upcoming import-maps one can resolve bare imports to different versions.

Unfortunately, for me and a lot of other developers that don't live on the edge, that is not feasable for now due to:

• target browser support, especially for features like import-maps which is still experimental
• only a small (but growing) set of third-party modules are published as ES modules
• those that do, have not yet agreed on:
  • oldest ES version to support
  • how much of the dependency tree comes bundled-in

This means that, even nowadays, using AMD as a module format for app extensions might be what we need, since:

• loaders can still support some non evergreen browsers, like IE11
• wide third-party module support, since they are very frequently published as UMD, which is compatible with the AMD spec
• not only that, but third-party UMD modules have become quite normalized:
  • usually transpiled down to ES5
  • they come bundled with every dependency except peer dependencies

Why bare-amd-loader and not X?

There are plenty of AMD loaders out there. After searching for the right one, I found out that they usually fall into 2 categories:

1. Complete, multi-purpose AMD loaders, like RequireJS, many of them fit for supporting Extendable Apps. But most of those features were built for the era that pre-dated bundlers, making the respective library much heavier then we need them too.
2. Small, laser-focused AMD loaders but that don't support bare module specifiers, which is a no-go since most of our day-to-day dependencies are named in that manner.

Given that the ecosystem wasn't catering for my specific requirements, I decided to build bare-amd-loader.

Local Development

Below is a list of commands you will probably find useful.

npm start

Runs the project in development/watch mode. Your library will be rebuilt if you make edits.

npm run build

Bundles the package to the dist folder. The package is optimized and bundled with Rollup into multiple formats (CommonJS, UMD, and ES Module).

npm test

Runs the test watcher (Jest) in an interactive mode. By default, runs tests related to files changed since the last commit.

Mentions

This project heavily relies on TSDX for overall tooling.

License

MIT license