babel-preset-jsy

0.15.3 verified Sat Apr 25 auth: no javascript maintenance

Babel preset for JSY, an indentation-based (offside) JavaScript syntax dialect that uses Python-like indentation instead of braces. This preset builds on babel-preset-env and supports Babel 6.x. It compiles JSY into standard JavaScript with automatic transpilation based on environment. The latest version is 0.15.3, with maintenance updates as needed. Unlike other indentation-based syntaxes such as CoffeeScript or LiveScript, JSY aims to stay close to standard JavaScript semantics while providing clean, whitespace-sensitive code. Current status is maintenance as JSY has limited adoption.

Common errors

error Error: Requires Babel "^6.0.0-0" but was loaded with "7.x.x". ↓

cause Using babel-preset-jsy with Babel 7 or later.

fix

Upgrade to a Babel 7 compatible preset or downgrade Babel to version 6.

error Error: Cannot find module 'babel-preset-jsy/lean' ↓

cause Incorrect path in preset configuration.

fix

Change preset to 'babel-preset-jsy/lean' or 'jsy/lean' depending on your setup.

error SyntaxError: Unexpected token (1:6) - using indentation ↓

cause Babel not configured to use the JSY preset.

fix

Add 'jsy/lean' to presets in your Babel config.

Warnings

deprecated This package is designed for Babel 6.x and may not work with Babel 7+. ↓

fix For Babel 7, consider using babel-plugin-jsy directly or look for updated presets.

breaking Version 0.10.0 changed the preset name from 'jsy' to 'jsy/lean'. ↓

fix Update your .babelrc: change "presets": ["jsy"] to "presets": ["jsy/lean"].

gotcha JSY syntax may conflict with standard JavaScript when used in mixed codebases. ↓

fix Use file extensions like .jsy or configure Babel to only transform JSY files if possible.

gotcha Cannot use both JSY and standard JavaScript in the same file without explicit transformation. ↓

fix Use babel-plugin-jsy with proper configuration to handle mixed syntax, or separate files.

Install

npm install babel-preset-jsy

yarn add babel-preset-jsy

pnpm add babel-preset-jsy

Imports

jsy
wrong
```
import { jsy } from 'babel-preset-jsy'
```
correct
```
module.exports = { presets: ['jsy/lean'] }
```
This is a Babel preset, not a JavaScript module. Use the preset name in Babel configuration as a string. 'jsy/lean' refers to a preset file inside the package.
babel-preset-jsy
wrong
```
require('babel-preset-jsy')
```
correct
```
const presets = ['babel-preset-jsy']
```
In Babel 6, presets are specified as strings in .babelrc or babel config. Doing 'require' returns an object, but Babel expects a function.
jsy/lean
```
const presets = ['jsy/lean']
```
The 'jsy/lean' preset is a variant that only transforms JSY syntax without additional polyfills or env targets.

Quickstart

Configures Babel with the jsy/lean preset and shows a sample JSY code snippet using indentation instead of braces.

// Install: npm install --save-dev babel-preset-jsy
// .babelrc configuration:
{
  "presets": ["jsy/lean"]
}

// Example JSY code (file.jsy)
// Indentation-based syntax
const add = (a, b) =>
  a + b

for (let i = 0; i < 10; i++)
  console.log(i)

if (true)
  console.log('true')
else
  console.log('false')

// Compile with: babel file.jsy