@zachsa/esm-x NPM

esm-x

Enhance browser-JavaScript support to include JSX/Typescript syntax for websites utilizing importmaps.

Motivation
- How it works
Usage
- Options
- Importmaps
  - External importmaps
Local development
- Publish
Install

Motivation

With all major browsers now supporting importmaps, bundle-free web development workflows have become both feasible and incredibly convenient. This project seeks to bring that convenience to React/Typescript projects.

How it works

Leverages importmaps in conjunction with the ES Module Shim library. With shimMode forced to true, all Source Code from the website origin is transpiled using Babel, while prior-optimized imports originating from a module CDN (such as the excellent JSPM CDN) are loaded directly.

Usage

Include the esm-x library (328kB gzipped) as the first script in your HTML file, and include at least one <script type="esm-x">...</script>. Scripts of type="esm-x" will be transpiled and executed in the order they are included in the HTML page.

Here is an example of a simple React application with the react and react-dom library imports defined via an importmap. Copy this file into index.html, and serve via a web server (i.e. npx http-server -c-1). There is an example of an @mui/material app in the test directory of this repository.

esm-x works without an importmap, but ES Module Shims is required.

<!doctype html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>ESM-X Example</title>

    <!-- Include ESM-X here -->
    <script
      id="esm-x"
      compiler="babel"
      loading="circular"
      src="https://www.unpkg.com/@zachsa/esm-x@1.0.32/dist/index.js"
    ></script>

    <!-- https://generator.jspm.io/#U2NhYGBiDs0rySzJSU1hKEpNTC7RTcnPdTC00DPSM9BPzslMzSuBiEPFAIy0jtgzAA -->
    <script type="importmap">
      {
        "imports": {
          "react": "https://ga.jspm.io/npm:react@18.2.0/index.js",
          "react-dom/client": "https://ga.jspm.io/npm:react-dom@18.2.0/client.js"
        },
        "scopes": {
          "https://ga.jspm.io/": {
            "react-dom": "https://ga.jspm.io/npm:react-dom@18.2.0/index.js",
            "scheduler": "https://ga.jspm.io/npm:scheduler@0.23.0/index.js"
          }
        }
      }
    </script>

    <!-- ES Module Shims -->
    <script
      async
      src="https://ga.jspm.io/npm:es-module-shims@1.9.0/dist/es-module-shims.js"
      crossorigin="anonymous"
    ></script>

    <!-- ESM-X script -->
    <script type="esm-x">
      import React, { FC } from 'react';
      import { createRoot } from 'react-dom/client';
      const root = createRoot(document.getElementById('root') as HTMLElement);

      const App: FC = () => <div>Hello from ESM-X</div>;
      root.render(<App />);
    </script>
  </head>
  <body>
    <div id="root"></div>
  </body>
</html>

Options

Configure the ESM-X script by including HTML tag id and other attributes:

<script id="esm-x" loading="circular|linear|disabled" compiler="babel|esbuild" src="..."></script>

Importmaps

Head to the JSPM generator to quickly generate an importmap. Any importmap configuration should be supported - huge importmaps are fine, make sure to take advantage of dynamic imports / code splitting (for example, Suspense/lazy when using React), etc. (and obviously don't preload scripts)

External importmaps

To use an external importmap, make sure that your importmap tag is of type "importmap-shim", and that the src url endsWith('importmap') || endsWith('importmap.json'). For example:

<script type="importmap-shim" src="path/to/file/called/importmap.json"></script>

It's easy to work with external importmaps using the jspm CLI.

Local development

Start a local web server and navigate to localhost:3000/test:

npx @mnemosyne/server -v ./
chomp --watch

Publish

npm publish --access public

Install

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