位置参照情報ダウンロードサービスからデータを落としてきて適当に整形して JSON にまとめる感じのやつ

run.js

// http://nlftp.mlit.go.jp/isj/agreement.html

const csv2json = require('csv2json');
const iconv = require("iconv-lite")
const fs = require('fs')
const path = require('path')

const items = fs.readdirSync(__dirname)
const promises = items.map(async (name) => {
  const filepath = path.join(__dirname, name)
  const stats = fs.statSync(filepath)
  if ( stats.isDirectory() === false ) return []
  const items = fs.readdirSync(filepath)

  const names = await Promise.all(items.map((name) => {
    if ( path.extname(name) !== '.csv' ) return undefined
    return path.join(filepath, name)
  }))
  return names
})

const stream = (filepath) => {
  return new Promise(resolve => {
    const datafilepath = path.join(path.dirname(filepath), path.basename(filepath, '.csv') + '.json')
    return resolve(datafilepath)
    fs.createReadStream(filepath)
      .pipe(iconv.decodeStream('windows-31j'))
      .pipe(csv2json())
      .pipe(fs.createWriteStream(datafilepath))
      .on('finish', () => {
        console.log('finish:', filepath)
        resolve(datafilepath)
      })
  })
}

Promise.all(promises)
  .then((items) => items.reduce((list, it) => list.concat(it), []).filter(it => it !== undefined))
  .then((names) => Promise.all(names.map(stream)).then((it) => it))
  .then(async (files) => {
    const stream = fs.createWriteStream('./result.json')
    stream.write('[')
    let total = files.length
    let nextSeparator = ''

    while ( files.length > 0 ) {
      const filepath = files.shift()
      const reader = fs.createReadStream(filepath, { encoding: 'utf8' })
      let buffer = ""

      const jsonChunk = (chunk) => {
        buffer += chunk
        while ( buffer.match(/{(?<content>.+)}/) !== null ) {
          const match = buffer.match(/{(?<content>.+)}/)

          const { index, groups } = match
          const { content } = groups
          buffer = buffer.substring(index + match[0].length)

          try {
            const raw = JSON.parse('{' + content + '}')
            const parsed = {
              prefecture: raw["都道府県名"],
              city: raw["市区町村名"],
              latitude: raw["緯度"],
              longitude: raw["経度"],
            }
            stream.write(nextSeparator + JSON.stringify(parsed), 'utf8')
            nextSeparator = ',\n'
          } catch (err) {
            console.error(content, err)
          }
        }
      }

      reader.on('data', jsonChunk)

      console.log('Start to import data from:', filepath)
      await new Promise(resolve => reader.on('end', () => resolve()))
      console.log('Finish to import data from:', filepath, total - files.length, '/', total)
    }

    stream.write(']')
    stream.end()
  })
  .then(() => process.exit(0))