Script Evaluation in Node.js

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 may or may not support.

• vm Node.js documentation
• MDN docs for eval
• Research for node-retrieve-globals.
• import("data:…") approach from 2ality.com
• import("blob:…") approach suggested by David Bushnell (not currently supported in Node.js but works in Deno!)

JavaScript Feature	Module#_compile	Function()	vm.Script	vm.Module	import("data:…")
Assign module.exports (CommonJS-only)	Yes	No	Yes	No5	No
export (ESM-only)	No	No	No	Yes1	Yes
require	Yes	Yes	Yes	Yes1	No
import (ESM-only)	No4	No4	No4	Yes1	No
Dynamic import()	Yes	Yes	Yes2	Yes1	No
Top level async or await	Faux3	Faux3	Faux3	Yes1	Yes
Can leak to global scope	Yes	Yes	No	No	Yes

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 I think that would cause more confusion than it’s worth.

Alternate methods

• A lot of the pain here is due to unstable vm.Module. If you already have access to a transpiler (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 to workaround this issue.
  • Some more discussion on Mastodon.