awaitable fs functions adapted from https://twitter.com/jamespearce/status/644002032479662080

example.js

import fs from 'fs'

import makeAwaitable from './makeAwaitable'

const fs2 = {
  open:  makeAwaitable(fs.open),
  write: makeAwaitable(fs.write),
  close: makeAwaitable(fs.close)
}

async function save (fileName, text) {
  const file = await fs2.open(fileName, 'w')
  
  await fs2.write(file, text)
  await fs2.close(file)
}

save('./test.txt', 'w00t!')

makeAwaitable.js

export const makeAwaitable = (fn) => {
  (...args) => new Promise((resolve, reject) => 
    fn.call(null, ...args, (err, ...args) => {
      err ? reject(err) : resolve(args)
    })
  )
}