Reverse proxy server for API + create-react-app (CRA)

package.json

{
  "name": "test",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "app": "concurrently \"node proxy-middleware.js\" \"npm start\"",
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test --env=jsdom",
    "eject": "react-scripts eject"
  },
  "dependencies": {
    "npm": "^6.4.1",
    "react": "^16.4.2",
    "react-dom": "^16.4.2",
    "react-router": "^4.3.1",
    "react-router-dom": "^4.3.1",
    "react-scripts": "1.1.4"
  },
  "devDependencies": {
    "concurrently": "^4.0.1",
    "express": "^4.16.3",
    "http-proxy-middleware": "^0.19.0"
  }
}

proxy-middleware.js

const express = require('express');
const proxy = require('http-proxy-middleware');

const proxyContexts = {
    react: {
        target: 'http://localhost:3000',
        //changeOrigin: true
    },
    api: {
        target: 'http://localhost:8080',
        //changeOrigin: true
    },
    prod: {
        target: 'https://my-prod.com',
        changeOrigin: true,
        onProxyRes: removeSecureCookieFlag
    }
};

/**
 * Remove "secure" flag from set-cookie header.
 * Insecure sites (http:) can't set cookies with the "secure" directive anymore (since Chrome 52+ and Firefox 52+).
 */
function removeSecureCookieFlag(proxyRes, req, res) {
    let existingCookies = proxyRes.headers['set-cookie'];
    let rewrittenCookies = [];

    if (existingCookies !== undefined) {
        if (!Array.isArray(existingCookies)) {
            existingCookies = [existingCookies];
        }
        for (let i = 0; i < existingCookies.length; i++) {
            rewrittenCookies.push(existingCookies[i].replace(/;\s*?(Secure)/i, ''));
        }
        proxyRes.headers['set-cookie'] = rewrittenCookies;
    }
}

// https://expressjs.com/en/4x/api.html#app.use
const app = express();

// Middleware functions are executed sequentially, therefore the order of middleware inclusion is important.

app.use('/api', proxy(proxyContexts.api));
app.use(proxy('ws://localhost:3000'));
app.use(proxy(proxyContexts.react));

// Static content if needed
// app.use(express.static('build'));

app.listen(3100);