Q:

I'm trying to serve my react app from express, why am I getting a 404?

I have a react app being built to my project's /dist directory, I'm trying to serve the bundle and required files via my express server, as well as connect to mongo and provide an api for some data there.
Right now I'm unable to get my app to load. I am getting an error GET http://localhost:5000/dist/bundle.js net::ERR_ABORTED 404 (Not Found) at localhost:5000
Below is my server file and the rest of the project is here
server.js:
require('dotenv').config();
const express = require('express');
const bodyParser = require('body-parser');
const mongoose = require('mongoose');
const routes = require('./routes/api');
const path = require('path');

const app = express();

const port = process.env.PORT || 5000;

//connect to the database
mongoose.connect('mongodb://localhost:27017/test', { useNewUrlParser: true })
  .then(() => console.log(`Database connected successfully`))
  .catch(err => console.log(err));

// overide mongoose promise (depricated) with node's promise
mongoose.Promise = global.Promise;

app.use((req, res, next) => {
  // TODO: should header be set on res or req?
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  next();
});

app.use(bodyParser.json());

app.use('/api', routes);

app.use((err, req, res, next) => {
  console.log(err);
  next();
});

app.get('/', function(req, res) {
  res.sendFile(path.join(__dirname + '/../index.html'));
});

app.use('/../dist', express.static('dist'));

app.listen(port, () => {
  console.log(`Server running on port ${port}`)
});

A:

Got it to work. Although I'd suggest switching over to my fullstack-mern-kit, but that's up for you to decide.
Anyway, follow these steps...
In the package.json change scripts to:
  "scripts": {
    "dev": "webpack-dev-server --config ./webpack.config.js --mode development",
    "build": "webpack --mode=production",
    "start": "node ./server.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },

In your dist folder, add an index.html (you'll also need include a <link> to your compiled css stylesheet):
<!DOCTYPE html>
<html>
  <head>
    <title>The Minimal React Webpack Babel Setup</title>
  </head>
  <body>
    <div id="app"></div>
    <script src="./bundle.js"></script>
  </body>
</html>

In your server.js file, rework it like so:
const express = require("express");
const app = express();
const { resolve } = require("path");

app.get("/sampleData", (req, res) => {
  res.send("sample data");
});

app.use(express.static("dist"));

app.get("*", (req, res) => res.sendFile(resolve("dist", "index.html")));

app.listen(8080);

Run npm run build, then npm start, then navigate to http://localhost:8080. 

