babel-preset-backpack

0.8.4 verified Sat Apr 25 auth: no javascript maintenance

Babel preset for Backpack projects, version 0.8.4 (final release, 2019). It configures Babel to target Node.js environments with ES6+ transpilation. Used internally by Backpack, but can be used independently. Key differentiators: includes specific plugins for Backpack's needs (async to generator, object rest/spread with useBuiltIns). Maintenance mode since 2019; no updates for Babel 8 or newer Node versions. Alternatives: @babel/preset-env.

Common errors

error Error: Cannot find module '@babel/core' ↓

cause Babel core is a required peer dependency of babel-preset-backpack and must be installed explicitly.

fix

Run: npm install --save-dev @babel/core

error SyntaxError: Unexpected token: punc (.) ↓

cause Preset uses plugins that may require older Babel 7 beta versions; using Babel 7 stable with preset 0.8.0 or 0.8.1 may cause incompatibilities.

fix

Upgrade babel-preset-backpack to >=0.8.1 which supports Babel 7 final, or use @babel/preset-env instead.

error Module build failed: Error: Plugin/Preset files are not allowed to export objects, only functions. ↓

cause Attempting to import babel-preset-backpack directly via require() in a JavaScript file rather than referencing it as a string in Babel config.

fix

Use the string 'backpack' in your Babel configuration (.babelrc, babel.config.js, etc.).

error WARNING: We noticed you're using the `useBuiltIns` option without declaring a core-js version. Currently, we assume version 2.x. ↓

cause Preset does not set a core-js version explicitly; Babel uses default core-js version 2.

fix

Specify core-js version in Babel config: { presets: [['backpack', { useBuiltIns: 'usage', corejs: 3 }]] } or install core-js@2.

Warnings

gotcha Requires @babel/core 7.x; incompatible with Babel 6.x and 8.x. ↓

fix Use @babel/core@^7.0.0 and ensure no Babel 6 packages are present.

deprecated This preset is effectively unmaintained since 2019. Backpack itself is no longer actively developed. ↓

fix Migrate to @babel/preset-env for modern projects.

breaking Version 0.8.0 introduced breaking changes moving from Babel 6 to Babel 7, and Webpack 3 to 4. ↓

fix Upgrade to 0.8.1 or later for compatibility with Babel 7 final releases.

gotcha Preset assumes Object.assign is available or polyfilled; does not include a polyfill itself. ↓

fix Use core-js or @babel/polyfill with useBuiltIns option if targeting older Node versions.

breaking Version 0.8.2 removed json-loader dependency, which may break Webpack configs that rely on it. ↓

fix If using Webpack <4, add json-loader explicitly to your Webpack config.

deprecated Preset includes transform-object-rest-spread (deprecated in Babel 7); use @babel/plugin-proposal-object-rest-spread instead. ↓

fix If you need to replicate behavior, manually add the plugin to your Babel config.

Install

npm install babel-preset-backpack

yarn add babel-preset-backpack

pnpm add babel-preset-backpack

Imports

babel-preset-backpack
wrong
```
require('babel-preset-backpack')
```
correct
```
module.exports = { presets: ['backpack'] }
```
Use as a string in Babel config; direct require is unnecessary.

useBuiltIns

wrong

use-built-ins

correct

{ presets: [['backpack', { useBuiltIns: 'entry' }]] }

Option name is camelCase, not kebab-case.

default
```
import preset from 'babel-preset-backpack' (but not recommended)
```
Direct import is possible but not standard; prefer string reference in Babel config.

Quickstart

Shows how to configure babel-preset-backpack in a .babelrc file, with or without options, and includes the required install command.

// .babelrc
{
  "presets": ["backpack"]
}

// or with options
{
  "presets": [
    ["backpack", { "useBuiltIns": "entry" }]
  ]
}

// install: npm install --save-dev babel-preset-backpack @babel/core @babel/plugin-proposal-object-rest-spread @babel/plugin-transform-async-to-generator