EnvironmentPlugin

The EnvironmentPlugin is shorthand for using the DefinePlugin on process.env keys.

Usage

The EnvironmentPlugin accepts either an array of keys or an object mapping its keys to their default values.

new webpack.EnvironmentPlugin(['NODE_ENV', 'DEBUG'])

This is equivalent to the following DefinePlugin application:

new webpack.DefinePlugin({
  'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV),
  'process.env.DEBUG': JSON.stringify(process.env.DEBUG)
})

Not specifying the environment variable raises an "EnvironmentPlugin - ${key} environment variable is undefined" error.

Usage with default values

Alternatively, the EnvironmentPlugin supports an object, which maps keys to their default values. The default value for a key is taken if the key is undefined in process.env.

new webpack.EnvironmentPlugin({
  NODE_ENV: 'development', // use 'development' unless process.env.NODE_ENV is defined
  DEBUG: false
})

Variables coming from process.env are always strings.

Unlike DefinePlugin, default values are applied to JSON.stringify by the EnvironmentPlugin.

To specify an unset default value, use null instead of undefined.

Example:

Let's investigate the result when running the previous EnvironmentPlugin configuration on a test file entry.js:

if (process.env.NODE_ENV === 'production') {
  console.log('Welcome to production');
}
if (process.env.DEBUG) {
  console.log('Debugging output');
}

When executing NODE_ENV=production webpack in the terminal to build, entry.js becomes this:

if ('production' === 'production') { // <-- 'production' from NODE_ENV is taken
  console.log('Welcome to production');
}
if (false) { // <-- default value is taken
  console.log('Debugging output');
}

Running DEBUG=false webpack yields:

if ('development' === 'production') { // <-- default value is taken
  console.log('Welcome to production');
}
if ('false') { // <-- 'false' from DEBUG is taken
  console.log('Debugging output');
}