Stream data from Mongoose into CSV download

mongoose-csv-stream-export.js

var Campaign = require('../model/campaign');

module.exports.getCampaignsCSV = function (req, res) {
  function CSVEscape(field) {
    return '"' + String(field || "").replace(/\"/g, '""') + '"';
  }
  
  var headers = [
    'Code-Nummer', //num
    'Kampagnenname', //name
    'Kampagnenquelle', //source
    'Kampagnenmedium', //medium
    'Kampagnenbegriff', //term
    'Kampagneninhalt' //content
  ].map(CSVEscape).join(',');

  function docToCSV(doc) {
    return [
      doc.num,
      doc.name,
      doc.source,
      doc.medium,
      doc.term,
      doc.content
    ].map(CSVEscape).join(',');
  }

  var started = false;
  function start(response) {
    response.setHeader('Content-disposition', 'attachment; filename=campaigns.csv');
    response.contentType('csv');
    response.write(headers + '\n');
    started = true;
  }

  Campaign.find()
  .sort('num')
  .stream()
  .on('data', function (campaign) {
    if (!started) { start(res); }
    res.write(docToCSV(campaign) + '\n');
  })
  .on('close', function () {
    res.end();
  })
  .on('error', function (err) {
    res.send(500, {err: err, msg: "Failed to get campaigns from db"});
  });
};

Newer code: https://gist.github.com/killercup/11256050