babel-plugin-dev

1.0.0 verified Sat Apr 25 auth: no javascript maintenance

Simple Babel plugin that replaces the global `__DEV__` identifier with `process.env.NODE_ENV !== 'production'`, allowing developers to conditionally include debug-only code without runtime overhead. Version 1.0.0 is stable and final; no new releases expected. It is lightweight with zero dependencies, works with Babel 6 and 7, and is used in production by many React-based libraries. Unlike alternatives like babel-plugin-transform-inline-environment-variables or manual if-blocks, this plugin provides a single-purpose, semantic `__DEV__` syntax with no configuration required.

Common errors

error Error: Cannot find module 'babel-plugin-dev' ↓

cause The package is not installed or is installed globally instead of locally.

fix

Run npm install babel-plugin-dev --save-dev in your project root.

error Error: __DEV__ is not defined ↓

cause The plugin is not applied or Babel compilation is not happening.

fix

Add 'dev' to your Babel plugins list (e.g., in .babelrc) and ensure you are compiling the file with Babel.

error SyntaxError: Unexpected token (1:10) > 1 | if (__DEV__) { ↓

cause The file is not being parsed by Babel (e.g., using node directly without transpilation).

fix

Make sure to run the file through Babel before execution, e.g., using @babel/node or a build step.

Warnings

gotcha The plugin replaces the global identifier `__DEV__` in all contexts, not just in variable declarations or expressions. ↓

fix Ensure `__DEV__` is not used as a variable name for other purposes; if you need scoped dev flags, use a different approach.

gotcha The replacement is textual and does not check for reassignment. If you assign `__DEV__ = false`, the replacement still occurs. ↓

fix Do not reassign `__DEV__`. Use it only as a read-only global flag.

deprecated This plugin is in maintenance mode. It works with Babel 6 and 7 but no new features are planned. ↓

fix Consider using @babel/plugin-transform-inline-environment-variables for more flexibility, or manually check process.env.NODE_ENV.

Install

npm install babel-plugin-dev

yarn add babel-plugin-dev

pnpm add babel-plugin-dev

Imports

default plugin
wrong
```
const plugin = require('babel-plugin-dev'); module.exports = { plugins: [plugin] }
```
correct
```
module.exports = { plugins: ['dev'] }
```
In .babelrc or babel.config.js, reference the plugin by its string name 'dev', not by requiring the package.

Programmatic usage with Babel core

wrong

const babel = require('babel-core'); babel.transform(code, { plugins: ['dev'] })

correct

const babel = require('@babel/core'); babel.transform(code, { plugins: ['dev'] })

For Babel 7, use @babel/core. For Babel 6, use babel-core. The plugin works with both.

CLI usage
wrong
```
babel --plugin babel-plugin-dev script.js
```
correct
```
babel --plugins dev script.js
```
Use the short name 'dev', not the full package name. Babel resolves the name automatically.

Quickstart

Configures Babel to replace __DEV__ with process.env.NODE_ENV !== 'production' for conditional debug code.

// File: test.js
const __DEV__ = true;
// In production, __DEV__ is replaced with process.env.NODE_ENV !== 'production'
if (__DEV__) {
  console.log('debug info');
}

// .babelrc
{
  "plugins": ["dev"]
}

// Run:
// npx babel test.js --plugins dev
// Output: if (process.env.NODE_ENV !== 'production') { console.log('debug info'); }