Express middleware to log request and response headers

app.js

const express = require('express')
const app = express()
const port = 3000

/**
 * Express middleware to log request and response headers
 */
app.use((req, res, nxt) => {
  const requestHeaders = req.headers

  console.log('Request Headers:', requestHeaders)

  // Request Headers: {
  //     'user-agent': 'PostmanRuntime/7.24.1',
  //     accept: '*/*',
  //     'cache-control': 'no-cache',
  //     'postman-token': '74416f71-0d09-453f-b714-3737dfd9f6b4',
  //     host: 'localhost:3000',
  //     'accept-encoding': 'gzip, deflate, br',
  //     connection: 'keep-alive'
  //   }

  res.on('finish', () => {
    const responseHeaders = res.getHeaders()

    console.log('Response Headers:', responseHeaders)

    // Response Headers: [Object: null prototype] {
    //     'x-powered-by': 'Express',
    //     'content-type': 'text/html; charset=utf-8',
    //     'content-length': '12',
    //     etag: 'W/"c-Lve95gjOVATpfV8EL5X4nxwjKHE"'
    //   }
  })

  nxt()
})

app.get('/', (req, res) => res.send('Hello World!'))

app.listen(port, () => console.log(`Listening at http://localhost:${port}`))

package.json

{
  "name": "express-req-res-headers",
  "version": "1.0.0",
  "description": "",
  "main": "app.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node ."
  },
  "keywords": [],
  "author": "abskmj@gmail.com",
  "license": "MIT",
  "dependencies": {
    "express": "^4.17.1"
  },
  "devDependencies": {
    "standard": "^14.3.3"
  }
}