baresm

Web service worker to resolve es6 bare module specifiers.

allows the use of npm installed package.json dependencies in node_modules as es6 module imports. eg.

index.html

<script type="module" src="index.mjs"></script>

index.mjs

import f, { n } from "some-lib";

f();
n();

why?

Browsers that support es6 module loading only do so with relative or absolute paths. package.json dependencies referenced in import statements will not be resolved by browsers. baresm.js will intercept bare module specifiers in javascript modules and rewrite them to absolute paths allowing you to use package.json dependencies in your module without any packaging / build stage of your code.

should I use this?

No. This is proof of concept and ultimately a stop-gap until browsers support bare module specifiers, if ever. The web specification for es6 module dependencies will likely look different to analyzing package.json files and resolving node_modules paths. Moreover, many typical/popular node_modules won't execute correctly without a packaging step directly in the browser and/or are very large and ultimatley unnecessary to deliver effectively your entire raw node_modules to browsers.

If you decide to use this:

• use HTTP/2, streams will make a huge difference for loading a ton of small files.
• ensure your dependencies can execute directly in the browsers you're targetting.
• reconsider using this

install

npm install --save baresm

copy baresm.js to your web root

if you web server supports following symlinks, create a symlink as a sibling to your index.html, ie

ln -s node_modules/baresm/baresm.js .

otherwise, copy:

cp node_modules/baresm/baresm.js .

index.html

<script>
  if ("serviceWorker" in navigator) {
    window.addEventListener("load", () => navigator.serviceWorker.register("/baresm.js?your-version"));
  }
</script>

replace your-version with a version token that reflects your module and/or dependency changes.

Alternatively use Service-Worker-Allowed header

have your index request serve Service-Worker-Allowed header as / so /node_modules/baresm/baresm.js may use the root scope /

Service-Worker-Allowed: /

index.html

<script>
  if ("serviceWorker" in navigator) {
    window.addEventListener("load", () => navigator.serviceWorker.register("/node_modules/baresm/baresm.js?your-version", { scope: "/" }));
  }
</script>

caching

baresm.js will create a node_modules cache key and will effectively cache any fetch requests for your origin that are Content-Type application/javascript. It is advised to version your service worker registration to ensure you reload this cache whenever you change your code and/or package dependencies.