Environment Variables

To disambiguate in your webpack.config.js between development and production builds you may use environment variables.

webpack's environment variables are different from the environment variables of operating system shells like bash and CMD.exe

The webpack command line environment option --env allows you to pass in as many environment variables as you like. Environment variables will be made accessible in your webpack.config.js. For example, --env.production or --env.NODE_ENV=local (NODE_ENV is conventionally used to define the environment type, see here.)

webpack --env.NODE_ENV=local --env.production --progress

Setting up your env variable without assignment, --env.production sets --env.production to true by default. There are also other syntaxes that you can use. See the webpack CLI documentation for more information.

There is one change that you will have to make to your webpack config. Typically, module.exports points to the configuration object. To use the env variable, you must convert module.exports to a function:

webpack.config.js

const path = require('path');

module.exports = env => {
  // Use env.<YOUR VARIABLE> here:
  console.log('NODE_ENV: ', env.NODE_ENV); // 'local'
  console.log('Production: ', env.production); // true

  return {
    entry: './src/index.js',
    output: {
      filename: 'bundle.js',
      path: path.resolve(__dirname, 'dist'),
    },
  };
};