mv test

generate.js

const fs = require('fs-extra');

async function main(size) {
  for (let i = 0; i < 5; i++) {
    console.log(i)
    let s = '';
    for (let j = 0; j < size; j++) {
      s += i
    }
    await fs.outputFile(`${i}.txt`, s)
  }
}

main(Number(process.argv[2]));

index.js

const fs = require('fs-extra')

const sleep = (time) => new Promise(resolve => setTimeout(resolve, time))

const wait = async (i) => {
  console.log(i)
  await fs.move(`${i}.txt`, 'out.txt')
  return i
}

const main = async () => {
  const idx = [0, 1, 2, 3, 4]

  const start = new Date()
  const values = await Promise.all(idx.map(wait))
  const end = new Date()
  const elapsed = (end - start) / 1000
  console.log(`dudation: ${elapsed} sec`)
}

main()

package.json

{
  "name": "mv-test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "cp ./tmp/*.txt . && node index.js",
    "generate": "node generate.js 10000000 && mkdir -p tmp && cp *.txt ./tmp",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "fs-extra": "^10.1.0"
  }
}