use-m: dynamically import any JavaScript module anywhere

use-m (m stands for module) is a utility for dynamically importing any JavaScript module (npm package) at runtime anywhere (browser or server).

It may be useful for standalone scripts that do not require a package.json. Also it may make your code portable across environments (for example it may require no changes in your code when executed in CommonJS, ES Modules and browser). You can ensure predictable behavior of your code over time by specifying the exact version to import directly in your script, similar to how versions are specified in package.json. You even can import multiple versions of the same library at the same time. You can use use-m when you don't want your package.json to be poluted with optional packages. You may keep your package.json with as little dependencies as needed thanks to use-m.

Table of Contents

- use-m: dynamically import any JavaScript module anywhere
- Table of Contents
- Key features
- Usage
- Universal
- Interactive shell in Node.js environment
- Browser
- Deno
- Bun
- Network imports
- Independent Scripts
- use-m and command-stream
- use-m and Bun.$
- use-m and zx
- use-m and execa
- Standard Import
- Installation
- CommonJS
- ES Modules
- Examples
- Questions and issues
- Contributing
- License

Key features

- Dynamic package loading: In node.js, use-m loads and imports npm packages on-demand with global installation (using npm i -g with separate alias for each version), making them available across projects and reusable without needing to reinstall each time. In case of a browser use-m loads npm packages directly from CDNs (by default esm.sh is used).
- Version-safe imports: Allows multiple versions of the same library to coexist without conflicts, so you can specify any version for each import (usage) without affecting other scripts or other usages (imports) in the same script.
- No more require, import, or package.json: With use-m, traditional module loading approaches like require(), import statements, and package.json dependencies become effectively obsolete. You can dynamically load any module at runtime without pre-declaring dependencies in separate file. This enables truly self-contained .mjs files that can effectively replace shell scripts.
- Built-in modules emulation: Provides emulation for Node.js built-in modules across all environments (browser, Node.js, Bun, Deno), ensuring consistent behavior regardless of the runtime.
- Relative path resolution: Supports ./ and ../ paths for loading local JavaScript and JSON files relative to the executing file, working seamlessly even in browser environments.

Usage

$3

Works in CommonJS, ES Modules and browser, and interactive environments.

``javascript
fetch('https://unpkg.com/use-m/use.js')
.then(async useJs => {
const { use } = eval(await useJs.text());
const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2) = ${_.add(1, 2)});
});
`

Universal execution comes at cost of eval usage, that is considered potential security threat. In case of this library only single file is evaled, it short, unminified and has no dependencies, so you can check the contents yourself. Once you have use function instance no more eval function will be executed by this library. If you don't want to use eval you can use await import() in browser or in node.js. In node.js you can also just install the package from npm as usual.

$3

1. Get the use function from use-m package:

Single line version:

`javascript
const { use } = eval(await (await fetch('https://unpkg.com/use-m/use.js')).text());
`

Formatted multiple version:

`javascript
const { use } = eval(
await (
await fetch(
'https://unpkg.com/use-m/use.js'
)
).text()
);
`


2. Import your favorite NPM package from the registry (for example lodash):
`javascript
const _ = await use('lodash@4.17.21');
`

3. Use your favorite function from dynamically imported package (for example add):
`javascript
_.add(1, 2)
`

Your output should be similar to the next screenshot.

$3

If you don't want to use eval in the browser, you can import use-m like this:

`javascript
const { use } = await import("https://esm.sh/use-m");
const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2) = ${_.add(1, 2)});
`

Only 2 lines and now have an interactive playground for JavaScript and almost any NPM library directly in your browser's console. No more cloud based sandboxes required. Sorry VSCode, you don't have such super powers yet.

$3

use-m works seamlessly with Deno! It automatically detects the Deno runtime and uses esm.sh as the default CDN.

`javascript
// Import use-m from CDN
const { use } = await import('https://esm.sh/use-m');

// Use any npm package
const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2) = ${_.add(1, 2)});

// Import multiple packages
const [lodash3, lodash4] = await use.all('lodash@3', 'lodash@4');
`

Run with Deno:
`bash
deno run --allow-net example.mjs
`

$3

use-m works seamlessly with Bun! It automatically detects the Bun runtime and provides optimized module loading.

`javascript
// Import use-m from CDN
const { use } = await import('https://esm.sh/use-m');

// Use any npm package
const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2) = ${_.add(1, 2)});

// Import multiple packages
const [lodash3, lodash4] = await use.all('lodash@3', 'lodash@4');
`

Run with Bun:
`bash
bun run example.mjs
`

$3

It is possible to use --experimental-network-imports to enable the same style of imports as in browser version. See the example.

1. Create file named example.mjs:
`javascript
const { use } = await import('https://unpkg.com/use-m/use.mjs');
const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2) = ${_.add(1, 2)});
`

2. Execute the script using --experimental-network-imports option:
`bash
node --experimental-network-imports example.mjs
`

$3

If you need to use use-m without adding it to a project locally, you can load it directly from unpkg using fetch. This is particularly useful for creating self-contained scripts without any package.json, node_modules, etc.

#### use-m and command-stream

command-stream is a modern shell utility library with streaming, async iteration, and EventEmitter support. It provides the most advanced command execution capabilities including virtual commands, built-in cross-platform commands, and real-time streaming.

1. Create a file named example.mjs:

`javascript
const { use } = eval(
await fetch('https://unpkg.com/use-m/use.js').then(u => u.text())
);

const { $ } = await use('command-stream');
const _ = await use('lodash');

// Use command-stream's advanced features
for await (const chunk of $ls -la.stream()) {
if (chunk.type === 'stdout') {
const files = chunk.data.toString();
console.log('Files:', _.filter(files.split('\n'), f => f.includes('.js')));
}
}

// Built-in cross-platform commands
await $mkdir -p build;
await $echo "Build complete" > build/status.txt;
`

2. Execute:

`bash
node example.mjs
`

#### use-m and Bun.$

Bun provides a built-in $ shell API that works seamlessly with use-m:

1. Create a file named example.mjs:

`javascript
#!/usr/bin/env bun

const { use } = eval(
await fetch('https://unpkg.com/use-m/use.js').then(u => u.text())
);

const _ = await use('lodash');

// Use Bun's built-in $ directly
const { stdout } = await $ls.pipe($grep js);
const files = _.filter(
_.split(stdout.toString(), '\n'),
(item) => !_.isEmpty(item)
);
console.log(files);
`

2. Execute with Bun:

`bash
bun run example.mjs
`

#### use-m and zx

1. Install zx globally

`bash
npm install -g zx
`

2. Create a file named example.mjs:

`javascript
#!/usr/bin/env zx --verbose

const { use } = eval(
await fetch('https://unpkg.com/use-m/use.js').then(u => u.text())
);

const _ = await use('lodash@latest');

const { stdout } = await $ls.pipegrep js;
const files = _.filter(
_.split(stdout, '\n'),
(item) => !_.isEmpty(item)
);
console.log(files);
`

3. Give execution permissions

`bash
chmod +x example.mjs
`

4. Execute:

`bash
./example.mjs
`

#### use-m and execa

1. Create a file named example.mjs:

`javascript
#!/usr/bin/env node

const { use } = eval(
await fetch('https://unpkg.com/use-m/use.js').then(u => u.text())
);

const _ = await use('lodash');
const { $: $$ } = await use('execa');
const $ = $$({ verbose: 'full' });

const { stdout } = await $ls.pipegrep js;
const files = _.filter(
_.split(stdout, '\n'),
(item) => !_.isEmpty(item)
);
console.log(files);
`

Note: in ES Module environments where __filename and require are not defined, you may need to add meta option into use function constructor, as it is not possible to access import.meta inside eval.

2. Execute:

`bash
node example.mjs
`

$3

You can still install and import use-m in node.js as usual. For example if you don't want to use eval in node.js.

#### Installation

Add use-m to your project with Yarn:

`bash
yarn add use-m
`

Or NPM:

`bash
npm i use-m
`

Load use-m to dynamically import the lodash package from npm:

#### CommonJS

`javascript
const { use } = require('use-m');

(async () => {
const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2) = ${_.add(1, 2)});
})();
`

or

`javascript
import('use-m')
.then(async ({ use }) => {
const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2) = ${_.add(1, 2)});
});
`

#### ES Modules

`javascript
import { use } from 'use-m';

const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2) = ${_.add(1, 2)});
`

or

`javascript
const { use } = await import('use-m');

const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2) = ${_.add(1, 2)});
``

Examples

You can check out usage examples source code. You can also explore our tests to get even more examples.

Questions and issues

If you have any questions or issues, please write us on GitHub. Together we can ensure this package will have highest quality possible. Your feedback is valuable and helps improve the project.

Contributing

We welcome contributions! To contribute please open Pull Request with any suggested changes.

License

This project is licensed under the Unlicense (public domain). That means you are absolutely free to use this library, there is no conditions or limitations on how this library and its code can be used.