Parse CSV, filter and then output to another file (e.g, Email)

parse-csv-email.js

const parse = require('csv-parse')
const fs = require('fs')
const transform = require('stream-transform')
const isEmail = require('is-email')


const input = fs.createReadStream('./input.csv')
const output = fs.createWriteStream('./output.csv')
const parser = parse({ delimiter: ',' })
const transformer = transform((record, callback) => {
  if (Array.isArray(record) && isEmail(record[4])) {
    callback(null, `${record[4]}\n`)
  } else {
    callback(null)
  }
}, { parallel: 5 })

input.pipe(parser).pipe(transformer).pipe(output)