Passing command line arguments to webpack.config.js

webpack.config.js can also exports a function of env which can return a conf object. You can therefore have a webpack config like:

module.exports = env => {
    return {
        entry: env === "production" ? "./app.js": "app-dev.js",
        output: {
          filename: "bundle.js"
        },
    }
};

and then call webpack from command-line (or package.json) like this:

webpack --env=production