babel-preset-proposals

0.4.0 verified Sat Apr 25 auth: no javascript maintenance

A Babel 7 preset that manages experimental proposal plugin dependencies, ordering, and default options. Current version 0.4.0 (released 2021-02-24), requires Node >=10. Key differentiators: automatically handles plugin ordering and option defaults for decorators and pipeline operator, removes plugins handled by @babel/preset-env, and supports all major TC39 proposals via boolean or object configuration. Release cadence is irregular; last release was over 3 years ago. Notable changes include removal of jsonStrings/nullishCoalescingOperator/optionalChaining options in v0.2.0 and addition of classStaticBlock in v0.4.0. This preset helps avoid common misconfigurations of Babel proposal plugins.

Common errors

error Error: [BABEL] unknown preset: 'babel-preset-proposals' ↓

cause Package not installed or not in node_modules path.

fix

Run 'npm install babel-preset-proposals' and ensure your .babelrc is in the project root.

error Error: Plugin .option is not a valid Plugin property ↓

cause Passed options not recognized by the preset, e.g., 'optionalChaining: true' in v0.2.0+.

fix

Check the README for valid options; for removed options, use @babel/preset-env or the plugin directly.

error TypeError: Cannot read property 'replace' of undefined ↓

cause Using preset with an invalid option value (e.g., passing a string instead of boolean/object).

fix

Ensure each option is either boolean or an Object as documented.

Warnings

breaking Removed options jsonStrings, nullishCoalescingOperator, optionalChaining; these plugins are now handled by @babel/preset-env (v0.2.0). ↓

fix Remove these options from preset config; enable via @babel/preset-env's targets or use the plugins directly if needed.

breaking Decorators default changed from {legacy: true} to no default; you must explicitly specify {legacy: true} to preserve old behavior (v0.2.0). ↓

fix Update preset config: replace 'decorators: true' with 'decorators: {legacy: true}' for legacy behavior.

breaking Node.js 8 required; dropped support for Node 6 (v0.3.0). v0.4.0 requires Node >=10. ↓

fix Upgrade Node.js to version 10 or higher for v0.4.0.

deprecated Some proposal plugins like classPrivateMethods and staticClassFeatures are not included; users must add them manually. ↓

fix Add missing plugins individually, e.g., @babel/plugin-proposal-private-methods.

gotcha Using absolutePaths: true is required if the config is used outside the project's node_modules scope; otherwise Babel may fail to resolve plugins. ↓

fix Set absolutePaths: true if generating config for external consumption or using with tools like Webpack's babel-loader.

Install

npm install babel-preset-proposals

yarn add babel-preset-proposals

pnpm add babel-preset-proposals

Imports

default
wrong
```
import preset from 'babel-preset-proposals'
```
correct
```
module.exports = require('babel-preset-proposals')
```
This is a CommonJS package; use require() in Node.js or configure in .babelrc/babel.config.js as a preset string.

validateOptions

wrong

import { validateOptions } from 'babel-preset-proposals'

correct

const { validateOptions } = require('babel-preset-proposals')

validateOptions is exported as a named export in CommonJS; destructure from require().

PresetOptions
wrong
```
import { PresetOptions } from 'babel-preset-proposals'
```
correct
```
// No TypeScript types shipped; define your own interface
```
This package does not provide TypeScript type definitions. You must create your own type for options.

Quickstart

Shows both .babelrc JSON configuration and programmatic CommonJS usage with options like classProperties, decorators, and loose mode.

// Install: npm install babel-preset-proposals
// .babelrc or babel.config.js
{
  "presets": [
    ["babel-preset-proposals", {
      "classProperties": true,
      "decorators": { "legacy": true },
      "exportDefaultFrom": true,
      "numericSeparator": true,
      "loose": true
    }]
  ]
}

// Programmatic usage (Node.js CJS):
const proposalsPreset = require('babel-preset-proposals');
const babel = require('@babel/core');
const result = babel.transformSync('code', {
  presets: [[proposalsPreset, { classProperties: true }]]
});
console.log(result.code);