Get size of piped STDIN in Node

stdin-bytes.js

#!/usr/bin/env node

// Borrowed and simplified from pretty-bytes by Sindre Sorhus
// https://github.com/sindresorhus/pretty-bytes/blob/main/index.js
function prettyBytes(num) {
  const UNITS = [
    'b',
    'kb',
    'mb',
    'gb',
    'tb',
  ]

  if (num === 0) return `0 ${UNITS[0]}`

  const exponent = Math.min(Math.floor(Math.log10(num) / 3), UNITS.length - 1)
  const unit = UNITS[exponent]
  const scaledNum = num / 1000 ** exponent

  return `${scaledNum.toLocaleString()} ${unit}`
}

let size = 0

process.stdin.on('data', (chunk) => {
  size += chunk.length
})

process.stdin.on('end', () => {
  console.log(prettyBytes(size))
})