node csv example

csv.js

const fs = require('fs');
// const csv = require('csv');

const { stringify } = require('csv-stringify');
const { parse } = require('csv-parse');
const { transform } = require('stream-transform');


async function readFromCSVFile(filename = 'read.csv') {
  const readStream = fs.createReadStream(filename);
  const rows = [];
  const parser = parse({
    columns: true,
    skip_empty_lines: true
  });
  return new Promise((resolve, reject) => {
    readStream.pipe(parser)
      .on("data", function (row) {
        rows.push(row);
      }).on("end", function () {
        resolve(rows);
      }).on("error", function (error) {
        reject(error);
      });
  });

}

async function writeToCSVFile(data = [], filename = 'write.csv') {
  const writeStream = fs.createWriteStream(filename);
  const columns = ['row', 'value'];
  const stringifer = stringify({ header: true, columns: columns });
  for (const row of data) {
    stringifer.write(row);
  }
  stringifer.pipe(writeStream);
}


async function transformCSV(readFilename = 'read.csv', writeFilename = 'write.csv') {
  const reader = fs.createWriteStream(readFilename);
  const writeStream = fs.createWriteStream(writeFilename);
  return reader
    .pipe(parse({ columns: true }))
    .pipe(transform((input) => {
      return Object.assign({}, input, {
        value: +input['value'] + 1
      });
    }))
    .pipe(stringify({ header: true }))
    .pipe(writeStream)
    .on('finish', () => {
      console.log('Done 🍻 ');
    });
}


async function main() {
  const records = new Array(100).fill(0).map((_, i) => ({ row: i, value: i }));
  const filename = '1.csv';
  await writeToCSVFile(records.map((item) => [item.row, item.value]), filename);
  console.log('Read csv file firstly  : ', await readCSVFile(filename));

  transformCSV(filename, '2.csv');
  readRecords = await readFromCSVFile(filename);
  console.log('Read csv file secondly : ', await readFromCSVFile(filename));
}

main().catch(console.error);