write a csv stream with json2csv

input.js

const { createReadStream, createWriteStream } = require('fs');
const { AsyncParser } = require('json2csv');

const fields = ['field1', 'field2', 'field3'];
const opts = { fields };
const transformOpts = { highWaterMark: 8192 };

// Using the promise API
const input = createReadStream(inputPath, { encoding: 'utf8' });
const asyncParser = new JSON2CSVAsyncParser(opts, transformOpts);
const parsingProcessor = asyncParser.fromInput(input);

parsingProcessor.promise()
  .then(csv => console.log(csv))
  .catch(err => console.error(err));

// Using the promise API just to know when the process finnish
// but not actually load the CSV in memory
const input = createReadStream(inputPath, { encoding: 'utf8' });
const output = createWriteStream(outputPath, { encoding: 'utf8' });
const asyncParser = new JSON2CSVAsyncParser(opts, transformOpts);
const parsingProcessor = asyncParser.fromInput(input).toOutput(output);

parsingProcessor.promise(false).catch(err => console.error(err));