file1.csv

file2.csv

file3.csv

process.js

'use strict';

const csv = require('csv');

const fs = require('fs'),
      PATH = require('path');

const _ = require('highland');

var seq = 0;

// write some value to the database, return a promise
function writeToDatabase(value) {
    console.log('writing value', value);
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            console.log('done writing', value);
            resolve(seq++);
        }, 100);
    });
}

_(fs.readdirSync('.'))
.flatten()
.filter(v => /\.csv$/.test(v))
.flatMap(v => {
    console.log('loading file:', v);

    let csvStream = fs.createReadStream(PATH.join(__dirname, v))
        .pipe(csv.parse());

    csvStream.once('end', function () {
        console.log('closed file:', v);
    });

    return _(csvStream).drop(1); // skip header row;
})
.flatMap(v => _(writeToDatabase(v)))
.each(v => { }) // consume the stream