concept web package manager
Last updated 10 months ago by chasemoskal .
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$ cnpm install importly 
SYNC missed versions from official npm registry.

???? importly ????

import map generator

importly is a command-line tool which generates import maps based on package.json dependencies

  1. install importly
    npm install -g importly

  2. generate an import map
    importly < package.json > importmap.json
    importly uses stdin/stdout/stderr
    pass in your package.json as input, and importmap.json will be the generated output

  3. importly will read the dependencies, and generate an importmap

    input: package.json

      "dependencies": {
        "lit-html": "^1.1.1",
        "lit-element": "^2.2.1"

    output: importmap.json

      "imports": {
        "lit-html/": "",
        "lit-html": "",
        "lit-element/": "",
        "lit-element": ""

    by default, the import map points to jsdelivr as the package host

  4. install the import map on your page via es-module-shims
    this amazing polyfill makes import maps work today!
    usage is basically like this

    <script defer src=""></script>
    <script type="importmap-shim" src="importmap.json"></script>
    <script type="module-shim">
      import {LitElement} from "lit-element"
  5. now get to work on your project!

    // thanks to the import map,
    // the browser can resolve this bare-specifier import!
    import {LitElement, html} from "lit-element"
    class MyElement extends LitElement {
      render() {

importly cli options

  • <stdin> (filestream)
    • any json5 file with a "dependencies" object
  • --lock (boolean)
    • whether or not to pin exact versions in the import map
    • default: true
  • --verbose (boolean)
    • whether or not to do some gross console logging
    • default: false
  • --host (string)
    • host from which to load packages in the browser
    • allows you to choose which 'generator' importly is using to generate the final import map
    • valid options: unpkg, jsdelivr, node_modules
    • default: jsdelivr
  • --lookup (string)
    • host from which to lookup package information (when importly is running)
    • allows you to choose which 'resolver' importly is using to query information about each package
    • sometimes unpkg or jsdelivr go down, so this option is handy to switch to the other
    • valid options: unpkg, jsdelivr
    • default: jsdelivr
  • <stdout> (filestream)
    • import map json file

the most useful option is probably the --host option, which allows you to set your local node_modules as the location from which to load packages

let's do the open source thing!

importly is experimental, and i'm open to new ideas!

so please, don't hesitate to contribute by opening new issues to ask questions, discuss ideas, question and even criticize! if you have any ideas, thoughts, or comments: i want to hear it, don't be shy!

  ???? Chase

so wait, why do we need import maps in the first place?

  • we're in the future ????️
  • we'll write modern es modules
  • we'll throw out our build step; no transpiling, no bundling
  • we'll use import maps to tell the browser where dependencies are
  • we'll use importly to generate those import maps

beyond bundling

  • in the traditional bundling ecosystem, we import stuff like this:

    import {render, html} from "lit-html"
      //                         ^
      //          this is called a "bare specifier" import
  • "import maps" is a browser feature allowing bare specifier imports directly in a <script type="module"> tag

  • so, the above bare specifier import would fail without the following import map

    <script type="importmap">
        "imports": {
          "lit-html/": "",
          "lit-html": "",

    and now the browser knows where to load lit-html when we import it ✔️

  • the only hitch, is that import maps are an upcoming browser feature — we need a polyfill!

  • so let's use guy bedford's amazing polyfill, es-module-shims, allows us to step into the future of import maps today!

  • i created importly to automatically generate the import maps

  ???? Chase

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