first-byte-time.js

// @ts-check
const https = require('https')

/**
 * @param {[number, number]} hrtime
 *
 * @returns {string}
 */
const parseHrtimeToSeconds = hrtime => (hrtime[0] + (hrtime[1] / 1e9)).toFixed(5)

const url = process.argv.pop()
console.info('Requesting %s ...', url)

const timings = {
  dns: '',
  tcp: '',
  tls: '',
  ttfb: '',
  total: ''
}
const start = process.hrtime()
const req = https.get(url, response => {
  response.once('readable', () => {
    timings.ttfb = parseHrtimeToSeconds(process.hrtime(start))
  })

  response.on('data', () => {})
  response.on('end', () => {
    timings.total = parseHrtimeToSeconds(process.hrtime(start))
  })

  response.on('close', () => console.table(timings))
})

req.on('socket', socket => {
  socket.on('lookup', () => {
    timings.dns = parseHrtimeToSeconds(process.hrtime(start))
  })
  socket.on('connect', () => {
    timings.tcp = parseHrtimeToSeconds(process.hrtime(start))
  })
  socket.on('secureConnect', () => {
    timings.tls = parseHrtimeToSeconds(process.hrtime(start))
  })
})

Usage:

node first-byte-time.js [URL]

Example:

node first-byte-time.js https://google.com