module-from-string

Load module from string using require or import.

Install

1npm install module-from-string

Usage

1import {
2  requireFromString,
3  importFromString,
4  importFromStringSync
5} from 'module-from-string'
6
7requireFromString("module.exports = 'hi'") // => 'hi'
8requireFromString("exports.greet = 'hi'") // => { greet: 'hi' }
9
10;(async () => {
11  await importFromString("export default 'hi'") // => { default: 'hi' }
12})()
13
14importFromStringSync(
15  "export const greet = Buffer.from([0x68, 0x69]).toString('utf8')",
16  { globals: { Buffer } }
17) // => { greet: 'hi' }

API

1import { Context } from 'vm';
2import { TransformOptions } from 'esbuild';
3
4interface Options {
5  filename?: string
6  dirname?: string
7  globals?: Context
8  useCurrentGlobal?: boolean
9}
10
11declare const requireFromString: (code: string, options?: Options) => any
12declare const createRequireFromString: (options?: Options) => typeof requireFromString
13
14interface ImportOptions extends Options {
15  transformOptions?: TransformOptions
16}
17
18declare const importFromString: (code: string, options?: ImportOptions) => Promise<any>
19declare const createImportFromString: (options?: ImportOptions) => typeof importFromString
20
21declare const importFromStringSync: (code: string, options?: ImportOptions) => any
22declare const createImportFromStringSync: (options?: ImportOptions) => typeof importFromStringSync

filename

Name, path or URL string of the virtual file for better exception stack trace.

1requireFromString(
2  "throw new Error('boom!')",
3  { filename: '/home/foo.js' }
4)
5// /home/foo.js:1
6// throw new Error('boom!')
7// ^
8//
9// Error: boom!
10//     at /home/foo.js:1:7
11//     at ...

dirname

Path or URL string of the directory for resolving require or import from relative path.

1requireFromString(
2  "module.exports = require('.')",
3  { dirname: path.join(__dirname, "../lib") }
4) // => require('../lib')

If not specified, the default value will be the current file's directory.

globals

Underneath the hood, module-from-string uses Node.js built-in vm module to execute code.

1// requireFromString
2
3vm.runInNewContext(
4  code,
5  {
6    __dirname: contextModule.path,
7    __filename: contextModule.filename,
8    exports: contextModule.exports,
9    module: contextModule,
10    require: contextModule.require,
11    ...globals
12  },

Take requireFromString for example, only the module scope variables are passed into the contextObject.

In order to use other global objects that are specific to Node.js, they need to be added to option globals or set option useCurrentGlobal to true.

1requireFromString(
2  'module.exports = process.cwd()',
3  { globals: { process } }
4) // => $PWD

Note: by default the built-in objects have a different prototype.

1const error = requireFromString('module.exports = new Error()')
2error instanceof Error // => false

useCurrentGlobal

Default to false. If set to true, all the available variables from the current global (or globalThis) are passed into the context.

transformOptions

Function importFromString and importFromStringSync can use esbuild to transform code syntax. See esbuild Transform API for documentation.

1const { greet } = importFromStringSync(
2  "export const greet: () => string = () => 'hi'",
3  { transformOptions: { loader: 'ts' } }
4)
5
6greet() // => 'hi'

ES modules

Dynamic import() expression of ES modules is supported by all three functions requireFromString, importFromString and importFromStringSync.

1;(async () => {
2  await requireFromString("module.exports = import('./index.mjs')")
3})()

import statement of ES modules is supported only by asynchronous function importFromString using Node.js experimental API vm.Module.

1node --experimental-vm-modules index.js
2
3# Or use environment variable
4NODE_OPTIONS=--experimental-vm-modules node index.js

1// with top-level await
2
3await importFromString("export { foo as default } from './index.mjs'")

License

MIT License © 2021 Exuanbo