es6-module-crosspiler

2.0.1 verified Fri May 01 auth: no javascript maintenance

An ES6 and CommonJS cross-compatible transpiler that enables mixed usage of ES6 modules and CommonJS modules during migration. Version 2.0.1 is the latest stable release but appears to be in maintenance mode as the project has seen no recent updates and uses legacy dependencies like recast and esprima-fb. Unlike higher-level transpilers (e.g., Babel), this is a lower-level library that operates on recast ASTs, allowing flexibility in custom build pipelines but lacking file system resolution and custom formatters.

Common errors

error SyntaxError: Unexpected token 'import' ↓

cause The JavaScript parser does not support ES6 module syntax (requires esprima-fb or similar).

fix

Use a custom esprima that supports ES6 modules, e.g., 'esprima-fb', when calling recast.parse().

error The module was imported incorrectly, e.g., using named import instead of default import. ↓

cause Attempting 'import { Module } from ...' instead of 'import Module from ...'

fix

Use default import: import Module from 'es6-module-crosspiler'

Warnings

breaking The library depends on 'esprima-fb', which is deprecated and may not support recent ES6 features. ↓

fix Use a more modern transpiler like Babel or TypeScript for ES6 module transpilation.

gotcha The default export handling differs from standard ES6 module semantics: CommonJS modules imported from ES6 modules are treated as default exports without the .default property. ↓

fix When cross-compiling, ensure that CommonJS modules do not export a .default property, as it will be overridden.

deprecated The package has not been updated since 2015 and uses deprecated dependencies like 'recast' and 'esprima-fb'. ↓

fix Migrate to a maintained transpiler such as Babel or esbuild.

gotcha The library requires explicit metadata for each dependency (.set() or constructor), otherwise it defaults to { type: 'module', default: false }. ↓

fix Always provide dependency metadata to avoid incorrect transpilation.

Install

npm install es6-module-crosspiler

yarn add es6-module-crosspiler

pnpm add es6-module-crosspiler

Imports

Module
wrong
```
const Module = require('es6-module-crosspiler').default
```
correct
```
import Module from 'es6-module-crosspiler'
```
The library uses a default export. In CommonJS, require returns the default export directly.

Module.transform

wrong

Module.transform(ast, { ... }) // incorrect: options should be passed as second argument

correct

Module.transform(ast, options)

Static convenience method; must be called on the Module class, not an instance.

Module.dependenciesOf

wrong

m.dependenciesOf(ast) // instance method does not exist; use static method

correct

Module.dependenciesOf(ast)

Static convenience method; returns an array of dependency names.

Quickstart

This shows how to transpile a simple ES6 import statement to CommonJS using recast, esprima-fb, and the crosspiler.

var recast = require('recast');
var esprima = require('esprima-fb');
var Module = require('es6-module-crosspiler');

var code = 'import { foo } from \'./lib\';';
var ast = recast.parse(code, { esprima: esprima });

var m = new Module(ast, {
  dependencies: {
    './lib': { type: 'module', default: false }
  }
});

var transformedAst = m.transform();
var result = recast.print(transformedAst);
console.log(result.code);