Export MongoDB Collection Data In CSV From Node Express Mongoose Application

Suppose a student collection in mongoDB have some data that we want to export in a CSV file from a Mongoose, Node, and Express app. For simplicity, let us assume only two fields in Mongoose schema: lastName and firstName. To export a CSV file, install moment, json2csv, and mongo-date-query (optional) npm packages:

npm install moment json2csv mongo-date-query --save

The required code is as follows:

'use strict';

const fs = require('fs');
const moment = require('moment');
const mdq = require('mongo-date-query');
const json2csv = require('json2csv').parse;
const path = require('path')
const fields = ['firstName', 'lastName'];
const Student = require('./student')

router.get('/', function (req, res) {
  Student.find({createdAt: mdq.lastYear()}, function (err, students) {
    if (err) {
      return res.status(500).json({ err });
    }
    else {
      let csv
      try {
        csv = json2csv(students, { fields });
      } catch (err) {
        return res.status(500).json({ err });
      }
      const dateTime = moment().format('YYYYMMDDhhmmss');
      const filePath = path.join(__dirname, "..", "public", "exports", "csv-" + dateTime + ".csv")
      fs.writeFile(filePath, csv, function (err) {
        if (err) {
          return res.json(err).status(500);
        }
        else {
          setTimeout(function () {
            fs.unlinkSync(filePath); // delete this file after 30 seconds
          }, 30000)
          return res.json("/exports/csv-" + dateTime + ".csv");
        }
      });

    }
  })
})

The breakdown of above code is:

Require fs to write file in export directory, moment to give a unique name to the file, json2csv to convert json to csv format, path to find exact path of directory for file temporary storage and Student Mongoose model
Define the fields we’re interested in exporting
Find students created last year
Convert student json response into csv with json2csv by passing fields as options
Define dateTime that includes date and time from year to seconds
Define file path of export
Write the csv file and respond the public link to it (The directory should be declared static in express server settings to be publicly available). The link will look like “/exports/csv-20180526052911.csv”, which the client (mobile/web app) can access and download by appending it to the base url of the server
Remove the file after a few seconds, as we’re not interested to keep the file in our directory indefinitely

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