Res

https://webpack.js.org/plugins/define-plugin/

Details

lets user define constants to be accessed in bundle

new webpack.DefinePlugin({
  PRODUCTION: JSON.stringify(true),
  VERSION: JSON.stringify("5fa3b9"),
  BROWSER_SUPPORTS_HTML5: true,
  TWO: "1+1",
  "typeof window": JSON.stringify("object")
})