Given a csv file with a column called "Category IDs" add a column called 'Category Names' with the name based on a lookup and write it out

catCodeReplace.js

const csv = require('csv')
const fs = require('fs')
const path = require('path')
const devnull = require('dev-null')

const catData = require('./catData')

const inputs = ['Members_49827_14.csv', 'Contacts Combined-3-Files.csv']

inputs.forEach(processCSV)

function processCSV (filename) {
  const parser = csv.parse({ columns: true })

  const transformer = csv.transform(function (record, callback) {
    record['Category Names'] = catLookup(record['Category IDs'])
    callback(null, record)
  },
  { parallel: 5 }
  )

  const stringify = csv.stringify({ header: true })

  fs.createReadStream(path.join(__dirname, filename), 'utf-8')
    .pipe(parser)
    .pipe(transformer)
    .pipe(stringify)
    .pipe(fs.createWriteStream(path.join(__dirname, filename + '.output.csv')))
}

function catLookup (data) {
  var cats = data.split(',') // Split the data by commas
  return dedupeArray(cats) // remove duplicates
    .map(function (code) { return lookupCode(code) }) // map runs the function for every item in the array
    .filter(function (cat) { return !!cat }) // filter out any categories that are blank (no match for teh code)
    .join(',') // join all the categories in the comma seperated list
}

function lookupCode (code) {
  code = parseInt(code)
  return catData[code] || ''
}

function dedupeArray (arr) {
  var seen = {}
  return arr.filter(function (item) {
    return seen.hasOwnProperty(item) ? false : (seen[item] = true)
  })
}