deploying create-react-app to heroku with express backend returns invalid host header in browser

Looks like they changed how the create-react-app utilizes a proxy. Remove the proxy from the package.json. Then...

Add this package:

npm i -S http-proxy-middleware

Then create a setupProxy.js in src:

src/setupProxy.js

const proxy = require("http-proxy-middleware");module.exports = app => {  app.use(proxy("/api/*", { target: "http://localhost:5000/" }));};

Now from inside the React component, you can do this:

src/App.js

import React, { Component } from "react";import logo from "./logo.svg";import "./App.css";export default class App extends Component {  state = {    message: "",    error: "",    eee: "",    text: ""  };  componentDidMount = () => this.fetchAPIMessage();  fetchAPIMessage = async () => {    try {      const res = await fetch(`/api/message`);      const { message } = await res.json();      this.setState({ message });    } catch (err) {      console.error(err);    }  };  render = () => (    <div className="App">      <header className="App-header">        <img src={logo} className="App-logo" alt="logo" />        <p>WELCOME CREATE REACT APP!</p>        <div className="App-link">{this.state.message}</div>      </header>    </div>  );}

index.js (I added npm i -D morgan which is a handy logging framework -- when a request hits the API, it displays it in the console).

const path = require("path");const express = require("express");const app = express();const morgan = require("morgan");app.use(morgan("tiny")); // logging framework// Serve our api messageapp.get("/api/message", async (req, res, next) => {  try {    res.status(201).json({ message: "HELLOOOOO FROM EXPRESS" });  } catch (err) {    next(err);  }});if (process.env.NODE_ENV === "production") {  // Express will serve up production assets  app.use(express.static("build"));  // Express will serve up the front-end index.html file if it doesn't recognize the route  app.get("*", (req, res) =>    res.sendFile(path.resolve("build", "index.html"))  );}// Choose the port and start the serverconst PORT = process.env.PORT || 5000;app.listen(PORT, () => console.log(`Mixing it up on port ${PORT}`));

package.json (use node to serve production assets -- see "start" script)

{  "name": "proxytest",  "version": "0.1.0",  "private": true,  "homepage": "https://proxytest2.herokuapp.com/",  "dependencies": {    "concurrently": "^4.0.1",    "express": "^4.16.4",    "http-proxy-middleware": "^0.19.0",    "react": "^16.5.2",    "react-dom": "^16.5.2",    "react-scripts": "2.0.5",    "serve": "^10.0.2"  },  "scripts": {    "start": "NODE_ENV=production node index.js",    "build": "react-scripts build",    "test": "react-scripts test",    "client": "react-scripts start",    "server": "nodemon server",    "eject": "react-scripts eject",    "dev": "concurrently --kill-others-on-fail \"npm run server\" \"npm run client\"",    "heroku-postbuild": "npm run build"  },  "eslintConfig": {    "extends": "react-app"  },  "browserslist": [    ">0.2%",    "not dead",    "not ie <= 11",    "not op_mini all"  ]}

What you'll see in the console when running in production:

m6d@m6d-pc:~/Desktop/proxytest-master$ npm start> proxytest@0.1.0 start /home/m6d/Desktop/proxytest-master> NODE_ENV=production node index.jsMixing it up on port 5000GET / 200 2057 - 6.339 msGET /static/css/main.068b9d02.chunk.css 304 - - 1.790 msGET /static/js/1.9a879072.chunk.js 304 - - 0.576 msGET /static/js/main.e3ba6603.chunk.js 304 - - 0.605 msGET /api/message 201 36 - 4.299 msGET /static/media/logo.5d5d9eef.svg 304 - - 0.358 ms

Other notes:

• Make sure to separate your client src from the API (for example, put everything from the front-end React application into a client folder with its own dependencies).
• Remove any and all React dependencies from your API's package.json