gistfile1.txt

const fs = require('fs')
const path = require('path')

const files = fs.readdirSync('.')

for (let file of files) {
  // fs.renameSync(file,)
  // console.log(file)
  let ext = path.extname(file)
  if (ext === '.JPG' || ext === '.JPEG') {
    // console.log(path.basename(file, ext))
    fs.renameSync(file, path.basename(file, ext) + '.jpg')
  }
}