Sync vs Async FS

result.txt

sync 3.8610219955444336
async 49.62050497531891

sync-vs-async.js

import { readFileSync } from 'node:fs'
import { open } from 'node:fs/promises'
import { performance } from 'node:perf_hooks'
import { strictEqual } from 'node:assert'

const lines = {sync: [], async: []}

{
  const start = performance.now()
  const file = ['./The-Gambler-by-Fyodor-Dostoyevsky.txt', 'utf8']
  lines.sync.push(...readFileSync(...file).split(/\r?\n/g))
  if (!lines.sync.at(-1)) {
    lines.sync.splice(lines.sync.length-1, 1)
  }
  console.log('sync', performance.now() - start)
}

{
  const start = performance.now()
  const handle = await open('./The-Gambler-by-Fyodor-Dostoyevsky.txt', 'r')
  for await (const line of handle.readLines()) {
    lines.async.push(line)
  }
  console.log('async', performance.now() - start)
}

strictEqual(lines.async.length, lines.sync.length)