start.js

'use strict'

const express = require('express')

const {resolve} = require('path')

const pkg = require('./package.json')

const app = express()



//The code below works because `.use` returns `this` which is `app`. So what we want to return in the `module.exports` is `app`, and we can chain on that declaration because each method invokation returns `app` after mutating based on the middleware functions
module.exports = app
  .use(express.static(resolve(__dirname, '.', 'public'))) // Serve static files from ../public

  .get('/*', (_, res) => res.sendFile(resolve(__dirname, '.', 'index.html')))  // Send index.html for any other requests.

  // notice the use of `_` as the first parameter above. This is a pattern for parameters that must exist, but you don't use or reference (or need) in the function body that follows.

if (module === require.main) {

  // Start listening only if we're the main module.

  /*
    https://nodejs.org/api/modules.html#modules_accessing_the_main_module
      - This (module === require.main) will be true if run via node foo.js, but false if run by require('./foo')
      - If you want to test this, log `require.main` and `module` in this file and also in `api.js`.
        * Note how `require.main` logs the same thing in both files, because it is always referencing the "main" import, where we starting running in Node
        * In 'start.js', note how `module` is the same as `require.main` because that is the file we start with in our 'package.json' -- `node server/start.js`
        * In 'api.js', note how `module` (this specific file - i.e. module) is different from `require.main` because this is NOT the file we started in and `require.main` is the file we started in
          ~ To help compare these objects, reference each of their `id` attributes
  */
  const server = app.listen(
    process.env.PORT || 3000,
    () => {
      console.log(`--- Started HTTP Server for ${pkg.name} ---`)
      console.log(`Listening on ${JSON.stringify(server.address())}`)
    }
  )
}