combine_csv.js

'use strict'
// const Promise = require('es6-promise').Promise;
const csv = require('csv-parse')
const fast = require('fast-csv');
const fs = require('fs')

const files = ['csv_1.csv', 'csv_2.csv']
const promises = []

files.forEach(file => {
  let promise = new Promise((resolve, reject) => {
    const data = []
    fs.createReadStream(`./csv/${file}`)
      .pipe(csv())
      .on('data', (record) => data.push(record))
      .on('error', (err) => reject(err))
      .on('finish', () => {
        resolve(data)
      })
  })
  promises.push(promise)
});

Promise.all(promises)
.then(values => {
  let t = []
  values.forEach((value, i) => {
    if (i != 0) value.shift()
    t = t.concat(value)
  })
  // console.log(t)
  let ws = fs.createWriteStream('./csv/all.csv')
  fast.writeToStream(ws, t, {headers: false})
  // fast.writeToString(t, {headers: true}, (err, data) => console.log(data))

})
.catch(err => console.log(err));

// p.then(
//   (value) => console.log(`good: ${value}`),
//   (error) => console.log(`error: ${error}`)
// )