scheme2js

1.4.2 verified Fri May 01 auth: no javascript

Version 1.4.2. A simple Scheme-to-JavaScript transpiler that converts Scheme expressions into JavaScript code. It supports basic Lisp constructs such as define, lambda, if, binary operations, and boolean expressions. The package includes a CLI tool (s2j) and a Node.js API. It features optional polyfill for pairs (cons, car, cdr). The library is lightweight and designed for educational purposes or small Scheme snippets. Release cadence is low, with no recent updates on GitHub.

Common errors

error const s2j = require('scheme2js') returns undefined ↓

cause The export might be a transpiled CommonJS module that does not export a default.

fix

Use const s2j = require('scheme2js').default or use ES module import.

error s2j(code) throws 'code is not a string' ↓

cause The function expects a string argument; passing a Buffer or other type will throw.

fix

Ensure the input is a string: s2j(String(code)).

error _ is not defined (after using pairs polyfill) ↓

cause The polyfill defines a helper `_` on the global object; if the code uses it before loading polyfill, references fail.

fix

Ensure --pairs is used at compile time and the resulting JavaScript file includes the polyfill at the top.

Warnings

gotcha The transpiler does not support all Scheme standards; it only handles a subset (define, lambda, if, binary ops, booleans). Complex macros or continuations will fail. ↓

fix Use only the documented constructs; refer to the README for supported features.

gotcha The `--pairs` flag adds a global polyfill for cons, car, cdr. This pollutes the global scope and may conflict with other libraries. ↓

fix Use the CLI without --pairs if you don't need pairs, or scope the polyfill manually.

gotcha The output uses `var` for definitions (e.g., `var foo = 1`). This may cause scoping issues in modern JavaScript contexts. ↓

fix Manually replace `var` with `let` or `const` after transpilation.

deprecated Require-style usage (const s2j = require('scheme2js')) is not deprecated but is not ESM-compatible. The package does not support ESM natively. ↓

fix Use ESM import syntax if your environment supports it.

Install

npm install scheme2js

yarn add scheme2js

pnpm add scheme2js

Imports

default
wrong
```
const s2j = require('scheme2js')
```
correct
```
import s2j from 'scheme2js'
```
ESM default import; CJS require works but is not the recommended pattern for modern usage.
default as named
wrong
```
import { s2j } from 'scheme2js'
```
correct
```
import s2j from 'scheme2js'
```
The module exports a single function as default; there is no named export.
type definitions
wrong
```
import { compile } from 'scheme2js'
```
correct
```
import s2j from 'scheme2js'
```
The library does not ship TypeScript types; use its default export only.

Quickstart

Transpile a Scheme factorial function to JavaScript using the API.

import s2j from 'scheme2js';

const schemeCode = `
  (define (factorial n)
    (if (eq n 0)
        1
        (* n (factorial (- n 1))))
`;

const jsCode = s2j(schemeCode);
console.log(jsCode);
// Output:
// function factorial(n) {
//   return eq(n, 0) ? 1 : n * factorial(n - 1);
// }