How to export csv nodejs

Here is what I did:

1. Use json2csv to build csv data from mongodb data

var json2csv = require('json2csv');
var fields = ['name', 'phone', 'mobile', 'email', 'address', 'notes'];
var fieldNames = ['Name', 'Phone', 'Mobile', 'Email', 'Address', 'Notes'];
var data = json2csv({ data: docs, fields: fields, fieldNames: fieldNames });

2. Send csv data to client

res.attachment('filename.csv');
res.status(200).send(data);

The json2csv package has been updated since the highest voted answer was written, the newer version has slightly different syntax:

        var { Parser } = require('json2csv')

        const fields = [{
            label: 'header 1',
            value: 'field1_name'
        }, {
            label: 'header 2',
            value: 'field2_name'
        }]

        const json2csv = new Parser({ fields: fields })

        try {
            const csv = json2csv.parse(data)
            res.attachment('data.csv')
            res.status(200).send(csv)
        } catch (error) {
            console.log('error:', error.message)
            res.status(500).send(error.message)
        }

res.attachment is a function and not an attribute. Needed to remove the equal sign for this to work.

Based on @VierTD answer, you have to use json2csv to build csv data from mongodb data.

Update Package.json with dependecies:

  "dependencies": {
    "mongodb": "^2.2.10",
    "json2csv": "*",
    "express": "*"
  }

Create the json2CSV object, remember this is mapping your document (db table) so names on "fields" must match db table, fieldNames are up to you but are also important since these are the CSV file column names:

var json2csv = require('json2csv');
var fields = ['name', 'phone', 'mobile', 'email', 'address', 'notes'];
var fieldNames = ['Name', 'Phone', 'Mobile', 'Email', 'Address', 'Notes'];
var data = json2csv({ data: docs, fields: fields, fieldNames: fieldNames });

Send csv data to the client:

res.attachment('filename.csv');
res.status(200).send(data);

This code shows how to export csv file based on mongo db document (database table)

I have created a github repo really brief sampling the idea, also created a database with dummy data at Mongo Lab Website so this code will run inmediately in your computer.Based on @VietTD answer.

In case you are interested on testing this code just remember to change following lines.

Change db url (User your own db this works but it's only for showing purposes).

        var url = 'mongodb://admin:[email protected]:63946/misale_dev';

Change target document (or db table).

var collection = db.collection('_dummy');

Change document columns (or db table's column fields):

var fields = ['_id', 'JobID', 'LastApplied'];

Finally set you CSV title column names as well as your CSV file name:

var fieldNames = ['ID_OR_PK', 'JOB_UNIQUE_ID_TITLE', 'APPLICATION_DATE'];

Last but not least:

res.attachment('yourfilenamehere.csv');

Please feel free to improve the sample code i'll appreciate that! or just download it and take a look at the code. It already comes with a database, so it will be easy to understand and run, in such a case you dont care here is the whole code maybe you see something interesting:

//
// EXPRESS JS SERVER INITI
//
var express = require('express')
var app = express()

//
// MONGO DB INIT
//
var MongoClient = require('mongodb').MongoClient, assert = require('assert');
app.get('/', function (req, res) {
    var url = 'mongodb://admin:[email protected]:63946/misale_dev';
    //
    // This function should be used for migrating a db table to a TBD format
    //
    var migrateMongoDBTable = function(db, callback) {
        // Get the documents collection
        console.log("Reading database records");
        // Get the documents collection
        var collection = db.collection('_dummy');
        // Find some documents
        //collection.find({'a': 3}).toArray(function(err, docs) {
        collection.find({}).toArray(function(err, docs) {
          assert.equal(err, null);
          //console.log(docs);
          //console.log('docs.length ---> ', docs.length);
          console.log('Creating CSV...');
          //console.log('-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-==-=');
          var json2csv = require('json2csv');
          var fields = ['_id', 'JobID', 'LastApplied'];
          var fieldNames = ['ID_OR_PK', 'JOB_UNIQUE_ID_TITLE', 'APPLICATION_DATE'];
          var data = json2csv({ data: docs, fields: fields, fieldNames: fieldNames });
          //console.log('-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-==-=');
          // EXPORT FILE
          res.attachment('yourfilenamehere.csv');
          res.status(200).send(data);
          callback(docs);
        });
    };

    // Use connect method to connect to the server
    MongoClient.connect(url, function(err, db) {
      assert.equal(null, err);
      console.log("Connected successfully to server");
      //
      // migrate db table to some format TBD
      //
      migrateMongoDBTable(db, function() {
        db.close();
      });
    });

})

app.listen(3000, function () {
  console.log('Example app listening on port 3000!')
})
// Connection URL
//var url = 'mongodb://localhost:27017/myproject';

I'm not totally sure what you're question is, but I think what you're looking for can be solved by setting the Content Disposition header. Take a look at this response on another another SO question: https://stackoverflow.com/a/7288883/2320243.

Using json2csv library you can export csv from mongodb data.

const json2csv = require('json2csv').parse;

//For unique file name
const dateTime = new Date().toISOString().slice(-24).replace(/\D/g, 
'').slice(0, 14); 

const filePath = path.join(__dirname, "../../../", "public", "exports", "csv-" 
+ dateTime + ".csv");

let csv; 

const student = await req.db.collection('Student').find({}).toArray();

// Logging student
// [{id:1,name:"John",country:"USA"},{id:1,name:"Ronny",country:"Germany"}]

const fields = ['id','name','country'];

 try {
    csv = json2csv(student, {fields});
 } catch (err) {
    return res.status(500).json({err});
 }

 fs.writeFile(filePath, csv, function (err) {
    if (err) {
        return res.json(err).status(500);
    }
    else {
        setTimeout(function () {
            fs.unlink(filePath, function (err) { // delete file after 30 sec
            if (err) {
                console.error(err);
            }
            console.log('File has been Deleted');
        });

    }, 30000);
        res.download(filePath);
    }
})

Real example maybe helpful

BACKEND - NodeJs

router.js

var { Parser } = require('json2csv');
const dataService = require('../service');

router.get('/exportData', cors(), async (req, res) => {
    const list = await dataService.getData(req);
    const fields = [
        { label: 'Id', value: 'Id' },
        { label: 'Name', value: 'Name' },
        { label: 'Age', value: 'Age' },
        { label: 'Date', value: 'Date' },
    ];
    const json2csv = new Parser({ fields: fields });
    const csv = json2csv.parse(list);
    res.status(200).send(Buffer.from(csv));
});

service.js

const sequelize = require('sequelize');
const moment = require('moment');
const { CallLogs } = require("../models");
const { Op } = sequelize;

exports.getData = async (req) => {
    let list = [];
    try {
        const { query: { Date_gte, Date_lt } } = req;
        const request = {
            where: {},
            order: [['Date', 'DESC']],
        };
        if (Date_gte && Date_lt) {
            request.where.Date = {
                [Op.between]: [Date_gte, Date_lt]
            }
        } else {
            if (Date_gte) {
                request.where.Date = {
                    [Op.gte]: Date_gte
                }
            }
            if (Date_lt) {
                request.where.Date = {
                    [Op.lt]: Date_lt
                }
            }
        }

        list = JSON.parse(JSON.stringify(await CallLogs.findAll(request)));

        list = list.map(c => {
            let obj = { ...c };
            obj.Date = moment(new Date(obj.Date)).format('DD.MM.YYYY');
            return obj;
        });
    } catch (error) {
        console.log(error);
    }
    return list;
}

FRONT END - REACT

app.js

import download from "downloadjs";
import Axios from "axios";

async function exportResultToExcel() {
    try {
        let filters = { ...this.state.filter };
        const res = (await Axios.get(`api/exportData`, {
            params: filters,
            responseType: "blob"
        })).data;
        if (res) {
            download(res, new Date().toLocaleDateString() + '-data.csv');
        } else {
            alert("Data not found");
        }
    } catch (error) {
        console.log(error);
    }
}

<Button onClick={() => { this.exportResultToExcel() }}>Export to CSV</Button>

Express-csv is a great module for writing csv contents to stream from a node.js server, which will be sent as a response to the client (and downloaded as a file). Very easy to use.

app.get('/', function(req, res) {
  res.csv([
    ["a", "b", "c"]
  , ["d", "e", "f"]
  ]);
});

The docs: https://www.npmjs.com/package/express-csv

When you pass an object, you need to prepend the headers explicitly (if you want them). Here's my my example using npm mysql

router.route('/api/report')
    .get(function(req, res) {
            query = connection.query('select * from table where table_id=1;', function(err, rows, fields) {
                if (err) {
                    res.send(err);
                }
                var headers = {};
                for (key in rows[0]) {
                    headers[key] = key;
                }
                rows.unshift(headers);
                res.csv(rows);
            });
    });

If you don't want to use a module, I would break it into two steps:

Step 1: Convert JSON to flat array

What's important here is that the JSON keys become the first row of the array

/**
 * Convert JSON list of objects to 2D array
 * Headers from first list item create first row of array
 * @param Array JSON list of objects
 * @return Array 2D array with first row as the object keys from the first object in list
 */
function json2array (data) {
  let headers = []
  let output = new Array(data.length + 1)
  // get object keys for first item if one exists
  if (data.length > 0) headers = Object.keys(data[0])
  output[0] = headers
  data.forEach((dataRow, row) => {
    const outputRow = new Array(headers.length)
    // populate array
    headers.forEach((header, column) => {
      outputRow[column] = dataRow[header]
    })
    output[row + 1] = outputRow
  })
  return output
}

// jsonData = [{email: "[email protected]", name: "John"}, {email: "[email protected]", name: "Jane"}] 

const arr = json2array(jsonData)

// arr = [["email", "name"],["[email protected]", "John"],["[email protected]", "Jane"]]

Step 2: Convert 2D array to CSV

Then you can save to file or output to browser, etc.

/**
 * Convert a 2D array into CSV notation
 * @param Array a 2D array with the first row as headers
 * @return String CSV-formatted text
 */
function array2csv (arr) {
  let csvOut = ''
  arr.forEach((arrRow, rowNum) => {
    let csvRow = ''
    arrRow.forEach((value, colNum) => {
      if (colNum > 0) csvRow += ',' // comma-separate columns
      const valueType = typeof(value)
      if (valueType == 'number') csvRow += value
      else if (valueType == 'boolean') csvRow += value ? 'TRUE':'FALSE'
      // quote strings and handle existing quotes
      else csvRow += '"' + value.replace(/"/g, '""') + '"'
    })
    if (rowNum > 0) csvOut += "\n" // newline-split rows
    csvOut += csvRow
  })
  return csvOut
}

const csvOut = array2csv(arr)

/*
"email","name"
"[email protected]","John"
"[email protected]","Jane"
*/

These methods are O(n) complexity.

I found a solution at this http://nikgrozev.com/2017/05/10/mongo-query-to-CSV-download-expressjs/

Keyword

stream the output to the HTTP response