Send CSV to client of in-memory data, without writing CSV on the server

CSVDownloadExample.js

// will generate CSV from  in-memory data 
// client will download as CSV without server having to save the file
//requries json2csv from npm

//ref: https://stackoverflow.com/questions/45922074/node-express-js-download-file-from-memory-filename-must-be-a-string

const json2csv = require('json2csv'); //from NPM
const stream = require('stream'); //Native Node

/*
Stuff
*/

let result = json2csv({
	data: data, 
	fields: [
		"Header1",
		"Header2",
		"Header3"
		]
});

let fileContents = Buffer.from(result);
let readStream = new stream.PassThrough();
readStream.end(fileContents);

res.set('Content-disposition', 'attachment; filename=' + 'roll.csv');
res.set('Content-Type', 'text/csv; charset=UTF-8');

readStream.pipe(res);