1.0.0 • Public • Published

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airdrop-cli is a package delivery tool for ES modules from npm packages. Use it to deliver packages from npm to the browser with no external connection needed at runtime.


  • Downloads and extracts packages from npm, including dependencies, into a flat file structure.
  • Optionally bundles packages, and dependencies, into a single ES module.
  • Generates a import-map compatible with the WICG import-maps proposal (and shims).
  • Provides a method to archive and merge downloaded packages and import-maps between systems.


$ npm install @swimlane/airdrop-cli -g

Or use npx @swimlane/airdrop-cli in place of airdrop in the examples below.

CLI Usage

Adding Packages

airdrop add <package> [<package>] [--force] [--bundle] [--optimize] [--clean]

The add command is optional; the default airdrop command is add.

  • <package>: npm package(s) (with optional version or tag) to add
  • --force: force add package(s) that have already been added
  • --bundle: bundle the added package(s)
  • --optimize: minify the generated bundle(s)
  • --clean: clean output directory before adding new packages
  • --no-color: disable CLI colors

The cli supports multiple packages and semantic version ranges. For example airdrop add lit-element es-module-shims@0.2.3 will install the latest version of lit-element and an exact version of es-module-shims.

Packages added using airdrop <package> are downloaded into a <package_path>/<name>@<version>/ directory. The same happens for each dependency of <package>. An import-map in the <package_path> directory is added or updated.

For example, running airdrop lit-element@2.0.1 results in a <package_path> directory structure of:

├── lit-element@2.0.1/
├── lit-html@1.0.0/
└── importmap.json

and an import-map of:

  "imports": {
    "lit-element@2.0.1": "<package_root>lit-element@2.0.1/lit-element.js",
    "lit-element@2.0.1/": "<package_root>lit-element@2.0.1/",
    "lit-element@2": "<package_root>lit-element@2.0.1/lit-element.js",
    "lit-element@2/": "<package_root>lit-element@2.0.1/"
  "scopes": {
    "lit-element@2.0.1": {
      "lit-html": "<package_root>lit-html@1.0.0/lit-html.js",
      "lit-html/": "<package_root>lit-html@1.0.0/"
    "lit-html@1.0.0": {}

The <package_path> directory is configurable via the package_path property in airdrop.config.js, the default is ./-/. In the generated import-maps, the package address is configurable via the package_root property, the default is /-/. This value must start with /, ../, or ./, or be an absolute URL.

The --bundle flag adds and bundles each <package> into a esm bundle (and with inlined dependencies) at <package_path>/<name>@<version>.bundle.js. The import-map is updated to resolve <name>@<version> to the bundle.

For example, running airdrop d3@5.9.2 --bundle results in a root directory structure of:

├── <d3 deps>
├── d3@5.9.2/
├── d3@5.9.2.bundle.js
└── importmap.json

and an import-map of:

  "imports": {
    "d3@5.9.2": "<package_root>d3@5.9.2.bundle.js",
    "d3@5": "<package_root>d3@5.9.2.bundle.js"
  "scopes": {}

Note that airdrop adds an import of the form <name>@<major-version> that resolves to the latest local version of the package.

Moving packages

Adding packages requires a connection to the npm registry. Once added an external connection is no longer required. The <package_path> directory can be deployed with other static assets or just manually copied between systems.

The following commands help move content from one system to another:

  • airdrop pack [<filename>] - Creates a tarball from the <package_path> directory. The <filename> is optional and defaults to using a timestamp.
  • airdrop merge <filename> - Unpacks a tarball to the <package_path> directory, merging the packed import-map with the existing import-map.

Other commands

  • airdrop init - Adds an airdrop.config.js to the current directory and an empty import-map.
  • airdrop version - Outputs the version number.
  • airdrop config - Displays current configuration.
  • airdrop clean - Cleans the output directory.
  • airdrop resolve <package> - Prints the resolved url for package(s).

In browser usage

Fixed Versions

The added ES modules can be loaded in the browser using a absolute path and full version.

  • /<package_root>/<name>@<version>[/file-path]

Use airdrop resolve <package> to find the resolved path.

<script type="module">
  import { html, render } from '/-/lit-html@1.0.0/lit-html.js';

Or with the dynamic import():

<script type="module">
    .then(({ html, render }) => {
      console.log(html, render);

Bare imports

While most modern browsers include support for ES modules, bare package specifiers are explicitly forbidden. In order to import bare package specifiers like import "lit-html" we need import-maps.

Note: import-maps are still an experimental specification. Use es-module-shims to polyfill most of the newer modules specifications. SystemJS also supports import-maps. However, SystemJS only loads System.register modules or AMD modules via extras.

<script type="module" src="/-/es-module-shims@0.2.3/dist/es-module-shims.js"></script>
<script type="importmap-shim" src="/-/importmap.json"></script>
<script type="module-shim">
  import { LitElement, css } from 'lit-element@2.1.0';
  import { html } from 'lit-html@1.0.0';

  class MyElement extends LitElement {
    static get properties() {
      return {
        mood: {type: String}
    static get styles() {
      return css`.mood { color: green; }`;
    render() {
      return html`Web Components are <span class="mood">${this.mood}</span>!`;

  customElements.define('my-element', MyElement);


Bundles can also be imported using fixed versions or bare imports when combined with the import-map.

<script type="module">
  import * as d3 from '/-/d3d3@5.9.2.bundle.js';
  d3.select('#hello').text('Hello World!!');
<script type="module" src="/-/es-module-shims@0.2.3/dist/es-module-shims.js"></script>
<script type="importmap-shim" src="/-/importmap.json"></script>
<script type="module-shim">
    import * as d3 from 'd3@5.9.2';
    d3.select('#hello').text('Hello World!!');



airdrop is a Swimlane open-source project; we believe in giving back to the open-source community by sharing some of the projects we build for our application. Swimlane is an automated cyber security operations and incident response platform that enables cyber security teams to leverage threat intelligence, speed up incident response and automate security operations.


MIT licensed.




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