The webpack treats your files differently in development mode from production mode. For one, your JavaScript files are all in-memory, that is, no files are actually written to the output directory, as specified here:

output: {
  path: helpers.root('dist')
  // other config is omitted
}

In development environments, we care about setting up source maps. Source maps remember what the file structure used to look like, before everything was concatenated into one or more bundles. It makes for easier debugging when the files resemble your project structure in your IDE. One way to set up source maps is to type the following:

devtool: 'cheap-module-eval-source-map'