module-from-string

module-from-string

Load module from string using require or import.

Install

npm install module-from-string

Usage

import {
  requireFromString,
  importFromString,
  importFromStringSync
} from 'module-from-string'

requireFromString("module.exports = 'hi'") // => 'hi'
requireFromString("exports.greet = 'hi'") // => { greet: 'hi' }

;(async () => {
  await importFromString("export default 'hi'") // => { default: 'hi' }
})()

importFromStringSync(
  "export const greet = Buffer.from([0x68, 0x69]).toString('utf8')",
  { globals: { Buffer } }
) // => { greet: 'hi' }

API

import { TransformOptions } from 'esbuild'

interface Options {
  dirname?: string
  globals?: Record<string, unknown>
}

interface ImportOptions extends Options {
  transformOptions?: TransformOptions
}

declare const requireFromString: (
  code: string,
  { dirname, globals }?: Options
) => any

declare const importFromString: (
  code: string,
  { dirname, globals, transformOptions }?: ImportOptions
) => Promise<any>

declare const importFromStringSync: (
  code: string,
  { dirname, globals, transformOptions }?: ImportOptions
) => any

dirname

An absolute path of the directory for resolving require or import from relative path.

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

// requireFromString

vm.runInNewContext(
  code,
  {
    __dirname: contextModule.path,
    __filename: contextModule.filename,
    exports: contextModule.exports,
    module: contextModule,
    require: contextModule.require,
    ...globals
  },

Take requireFromString for example, only the above variables are passed into the contextObject. In order to use other global objects and built-in modules you need to add them to option globals.

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

transformOptions

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

const { greet } = importFromStringSync(
  "export const greet: () => string = () => 'hi'",
  { transformOptions: { loader: 'ts' } }
)

greet() // => 'hi'

ES modules

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

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

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

node --experimental-vm-modules index.js

# Or use environment variable
NODE_OPTIONS=--experimental-vm-modules node index.js

// with top-level await

await importFromString("export { foo as default } from './index.mjs'")

License

MIT License © 2021 Exuanbo

Changelog

3.1.0 (2021-08-21)

Bug Fixes

• Fix problem when using import statement of ES modules.

Features

• Add new optional option dirname to specify the directory path for resolving relative path require or import.
• Add support for dynamic import() expression.