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.

If an environment variable is not found during bundling and no default value was provided, webpack will throw an error instead of a warning.

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');
}

Use Case: Git Version

The following EnvironmentPlugin configuration provides process.env.GIT_VERSION (such as "v5.4.0-2-g25139f57f") and process.env.GIT_AUTHOR_DATE (such as "2020-11-04T12:25:16+01:00") corresponding to the last Git commit of the repository:

const child_process = require('child_process');
function git(command) {
  return child_process.execSync(`git ${command}`, { encoding: 'utf8' }).trim();
}

new webpack.EnvironmentPlugin({
  GIT_VERSION: git('describe --always'),
  GIT_AUTHOR_DATE: git('log -1 --format=%aI'),
});

DotenvPlugin

The third-party DotenvPlugin (dotenv-webpack) allows you to expose (a subset of) dotenv variables:

// .env
DB_HOST=127.0.0.1
DB_PASS=foobar
S3_API=mysecretkey

new Dotenv({
  path: './.env', // Path to .env file (this is the default)
  safe: true // load .env.example (defaults to "false" which does not use dotenv-safe)
});