Momentjs to Dayjs locale importer

localeimporter.js

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

const momentLocaleFolder = path.join(__dirname, 'locale')
const dayjsLocaleFolder = path.join(__dirname, 'src/locale')
const saveFolder = path.join(__dirname, 'src/locale')
const Moment = require(path.join(__dirname, './moment'))

function objectToString(obj, prefix = '  ') {
  let string = '{'
  Object.keys(obj).forEach((p, i) => {
    const str = JSON.stringify(obj[p])
    if (str) string += `\n${prefix}${p}: ${str}${i < Object.keys(obj).length - 1 ? ',' : ''}`
  })
  string += '\n},'
  return string
}

fs.readdirSync(momentLocaleFolder).forEach((file) => {
  const filePath = path.join(momentLocaleFolder, file)
  require(filePath)
  const momentLocaleRelativeTime = Moment[file.replace('.js', '')].relativeTime
  const momentLocaleFormats = Moment[file.replace('.js', '')].longDateFormat
  delete momentLocaleRelativeTime.ss

  const dayjsFilePath = path.join(dayjsLocaleFolder, file)
  const dayjsFile = fs.readFileSync(dayjsFilePath, 'utf-8')
  const oldLocale = dayjsFile.split('const locale = ')[1].split('dayjs.locale')[0]

  let toBeAdded = ''
  if (oldLocale.indexOf('formats') < 0) {
    toBeAdded += `formats: ${objectToString(momentLocaleFormats)}\n  `
  }

  if (oldLocale.indexOf('relativeTime') < 0) {
    toBeAdded += `relativeTime: ${objectToString(momentLocaleRelativeTime)}\n  `
  }

  const start = oldLocale.substring(0, oldLocale.lastIndexOf('}'))
  const end = oldLocale.substring(oldLocale.lastIndexOf('}'), oldLocale.length)
  const localeToWrite = `${start}${toBeAdded ? ',' : ''}${toBeAdded}${end}`

  const saveLocalePath = path.join(saveFolder, file)
  fs.writeFileSync(saveLocalePath, `import dayjs from 'dayjs'

const locale = ${localeToWrite}dayjs.locale(locale, null, true)

export default locale

`)
})

// Copy momentjs locales folder to `locale` folder in dayjs root
// Create dummy `moment.js` with contents
// module.exports = {
//  defineLocale(name, val) {
//    this[name] = val
//  }
// }
// Change `saveFolder` if you want to test before overwriting original files in dayjs