Get hash and filesize in stream

get-file-hash-and-size-in-stream.js

const fs = require('fs')
const crypto = require('crypto')

const getHashAndSize = (file, alg = 'sha1') => new Promise((resolve, reject) => {
  let size = 0
  const hasher = crypto.createHash(alg, { encoding: 'hex' })
  const filestream = fs.createReadStream(file)

  filestream.pipe(hasher)
  filestream.on('data', (d) => { size += d.length })
  filestream.on('end', () => {
    hasher.end()
    const hash = hasher.read()
    
    return resolve({ hash, size })
  })
})