import-module-string

import-module-string

Use import('data:') and import(Blob) to execute arbitrary JavaScript strings. A simpler alternative to node-retrieve-globals that works in more runtimes.

Installation

Available on npm as import-module-string.

npm install import-module-string

Features

• Multi-runtime: tested with Node (18+), Deno (limited), Chromium, Firefox, and WebKit.
• Defers to export when used, otherwise implicitly export all globals (via var, let, const, function, Array or Object destructuring assignment, import specifiers, etc)
• Supports top-level async/await (as expected for ES modules)
• Emulates import.meta.url when filePath option is supplied
• addRequire option adds support for require() (in Node)
• Extremely limited dependency footprint (acorn for JS parsing only)
• Supports data object to pass in data (must be JSON.stringify friendly, more serialization options may be added later)
• Subject to URL content size maximums: Chrome 512MB, Safari 2048MB, Firefox 512MB, Firefox prior to v137 32MB

Feature	Server	Browser
import('./file.js')	✅	✅ (Import Map-friendly)
import('bare')	✅	✅ (Import Map-friendly)
import('built-in')	✅	N/A
require()	✅ with addRequire option	❌
import.meta.url	✅ with filePath option	✅ with filePath option

Notes:

• built-in modules are provided by the JavaScript runtime. node:fs is one example.
• bare specifiers are packages referenced by their bare name. In Node this might be a package installed from npm.

Usage

Import the script first!

import { importFromString } from "import-module-string";

View the test suite file for more examples.

Export

await importFromString(`export var a = 1;
export const c = 3;
export let b = 2;`);

// Returns
{ a: 1, c: 3, b: 2 }

No export

import { importFromString } from "import-module-string";

await importFromString(`var a = 1;
const c = 3;
let b = 2;`);

// Returns
{ a: 1, c: 3, b: 2 }

Pass in data

await importFromString("const a = b;", { data: { b: 2 } });

// Returns
{ a: 2 }

Pass in filePath

await importFromString("const a = import.meta.url;", { filePath: import.meta.url });

// Returns value for import.meta.url, example shown
{ a: `file:///…` }

Imports (experimental feature)

Relative references

// `dependency.js` has the content `export default 2;`
await importFromString("import dep from './dependency.js';");

// Returns
{ dep: 2 }

Bare references

Uses import.meta.resolve to resolve paths, which will also resolve using Import Maps (where available).

// maps with `import.meta.resolve("@zachleat/noop"))` in-browser (Import Map friendly)
await importFromString("import {noop} from '@zachleat/noop';");

// Returns
{ noop: function() {} }

Builtins

await importFromString("import fs from 'node:fs';");

// Returns (where available: `node:fs` is not typically available in browser)
{ fs: { /* … */ } }

As a side note, you can shim fs into the browser with memfs.

Changelog

• v2.0.0 removes adapter (no longer necessary!)
• v1.0.5 bug fixes
• v1.0.4 add adapter option (add adapter: "fs" or adapter: "fetch") to resolve imports in various environments.