https://github.com/zachleat/javascript-eval-modules

Playground for testing various dynamic script execution methods in JavaScript
https://github.com/zachleat/javascript-eval-modules

Last synced: 9 months ago
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Playground for testing various dynamic script execution methods in JavaScript

• Host: GitHub
• URL: https://github.com/zachleat/javascript-eval-modules
• Owner: zachleat
• Created: 2024-09-19T19:39:26.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2025-06-05T21:43:44.000Z (about 1 year ago)
• Last Synced: 2025-06-05T22:23:58.066Z (about 1 year ago)
• Language: JavaScript
• Homepage:
• Size: 27.3 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

          
# Dynamic Script Evaluation in JavaScript

You have a `String` of JavaScript code. How can you execute it? This is a playground for testing various dynamic script execution methods in Node.js and what features they support.

This is research for [`import-module-string`](https://github.com/zachleat/import-module-string) (the approach I currently use and recommend for ESM code) and [`node-retrieve-globals`](https://github.com/zachleat/node-retrieve-globals/) (legacy but more CommonJS friendly), whose features I have documented in a separate compatibility table below.

* [`vm` Node.js documentation](https://nodejs.org/docs/latest/api/vm.html)

* [MDN docs for `eval`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval)

* [`import("data:…")` approach from `2ality.com`](https://2ality.com/2019/10/eval-via-import.html)

* [`import("blob:…")` approach suggested by David Bushnell](https://github.com/dbushell/dinossr/blob/main/src/bundle/import.ts#L13) (not currently supported in Node.js but works in Deno!)

## Runtime Native Methods

  

    

      JavaScript Feature

      Module#_compile

      Function()

      vm.Script

      vm.Module

      import("data:…") (or blob:…)

    

  

  

    

      Assign module.exports (CommonJS-only)

      Yes

      No

      Yes

      No5

      No

    

    

      export (ESM-only)

      No

      No

      No

      Yes1

      Yes

    

    

      require

      Yes

      Yes

      Yes

      Yes1

      No6

    

    

      import (ESM-only)

      No4

      No4

      No4

      Yes1

      No7

    

    

      Dynamic import()

      Yes

      Yes

      Yes2

      Yes1

      No7

    

    

      Top level async or await

      Faux3

      Faux3

      Faux3

      Yes1

      Yes

    

    

      Can leak to global scope

      Yes

      Yes

      No

      No

      Yes

    

    

      Runtime Compatibility

      Node.js

      Any

      Node.js

      Node.js

      Any

    

  

Notes:

1. Requires `--experimental-vm-modules`. Use outputs an `ExperimentalWarning` to the console.

2. Requires `vm.constants.USE_MAIN_CONTEXT_DEFAULT_LOADER` an experimental Node feature added in v21.7.0, v20.12.0. Any use outputs an `ExperimentalWarning` to the console.

3. Requires the code to be wrapped in an `(async () => {})()` IIFE wrapper.

4. Can use `esm-import-transformer` to transform static `import` to dynamic `import()` or `require`: https://github.com/zachleat/esm-import-transformer

5. Probably shimmable but not worth it.

6. `require` is shimmable in Node.js via [`node:module#createRequire`](https://nodejs.org/docs/latest/api/module.html#modulecreaterequirefilename)

7. `import` of runtime built-ins (e.g. `node:` prefixed modules in Node.js) are allowed.

## npm Packages

  

    

      JavaScript Feature

      npm:node-retrieve-globals

      npm:import-module-string

    

  

  

    

      Assign module.exports (CommonJS-only)

      Yes

      No

    

    

      export (ESM-only)

      No

      Yes

    

    

      require

      Yes

      Yes

    

    

      import (ESM-only)

      No

      Yes

    

    

      Dynamic import()

      Yes

      Yes

    

    

      Top level async or await

      Faux3

      Yes

    

    

      Can leak to global scope

      Yes

      Yes

    

    

      Runtime Compatibility

      Node.js

      Any

    

  

## Alternate methods

* A lot of the pain here is due to an experimental `vm.Module`. If you already have access to a bundler (e.g. `esbuild`), use that to output CommonJS code and run it through `Module#_compile` to bypass current limitations with dynamic ESM in Node.js.

	* [Vite writes a temporary file to the filesystem](https://github.com/vitejs/vite/blob/77d5165e2f252bfecbb0eebccc6f04dc8be0c5ba/packages/vite/src/node/config.ts#L1172-L1184) to workaround this issue.

	* Some [more discussion on Mastodon](https://fediverse.zachleat.com/@zachleat/111580482330587997).