Loads ES modules with CJS interop in Node

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0.3.87 years ago8 years agoMinified + gzip package size for node-es-module-loader in KB


NodeJS ES Module Loader
Loads ES modules and WebAssembly with CJS interop in Node, roughly according to
WASM support is currently only provided for Node 8 nightly.
Follows the NodeJS resolution algorithm, loading modules first as CJS and then falling back to ES on import or export syntax failures. This effectively provides the "export {}" assumption to load an ES module.
This does mean a double-parse, over the mjs approach currently being taken by Node.
Built with the ES Module Loader polyfill 1.0 branch at


npm install -g node-es-module-loader


Execute an ES module file:
node-esml module.js

For example, where module.js contains:
import fs from 'fs';
import {fn} from './local-es-module.js';
import {wasmFn} from './local-wasm-binary.wasm';

Note that only the default import form for CommonJS modules is supported.
Also supports dynamic loading via the dynamic import syntax:
export function lazyLoad(path) {
  return import(path);

Source maps for errors are fully supported through the source-map-support project.
Source maps also work in Node 6 with the node --inspect flag via:
node --inspect node_modules/.bin/node-esml module.js

Programmatic Usage

var NodeESModuleLoader = require('node-es-module-loader');

var loader = new NodeESModuleLoader(/* optional basePath */);

loader.import('x').then(function(m) {
  // ...


  • Does not currently support the "module" package.json proposal described in the second paragraph at
  • Does not allow any loading of ES modules from within CommonJS itself
  • Does not implement global require filtering described in
  • Does not provide CJS exports as named exports, skipping the algorithm defined in this may change, pending Node implementation intentions
Alternative Babel options can be set with a local .babelrc file.