Download CouchDB(PouchDB) database documents as excel file

server.js

const express = require("express");
const fs = require('fs');
const expressPouchDB = require("express-pouchdb");
const PouchDB = require("pouchdb");
const ExcelJS = require('exceljs');
const moment = require('moment');

const app = express();
const port = 8080;

app.use(express.static("build"));
app.use(express.json());

app.use('/db', expressPouchDB(PouchDB));

app.get('/download/excel/:database', (req, res) => {
    let db = new PouchDB(`http://127.0.0.1:${port}/db/${req.params.database}`, { skip_setup: true });
    let fields = [];
    let header, worksheet, workbook;

    db.info().then(() => {
        workbook = new ExcelJS.Workbook();
        worksheet = workbook.addWorksheet("Results");
        header = worksheet.addRow();
        return db.allDocs({ 'include_docs': true });
    }).then(results => {
        fs.writeFileSync("test.json", JSON.stringify(results));
        for (let i in results.rows) {
            let doc = results.rows[i]['doc'];
            delete (doc['_id']);
            delete (doc['_rev']);
            let row = worksheet.addRow();
            //Date field
            if (doc.submitted) {
                let submitted = moment(doc.submitted);
                doc.submitted = submitted.add(submitted.utcOffset(), 'minutes').toDate();
            }
            for (let field in doc) {
                if (fields.indexOf(field) === -1) {
                    fields.push(field);
                }
                row.getCell(fields.indexOf(field) + 1).value = doc[field];
            }
        }
        fields.forEach((field, index) => {
            let cell = header.getCell(index + 1);
            cell.value = field;
            cell.fill = {
                type: 'pattern',
                pattern: 'solid',
                fgColor: { argb: 'ffcccccc' }
            };
            cell.font = {
                bold: true
            }
        });
        res.setHeader("Content-Type", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
        res.setHeader('Content-Disposition', `attachment; filename="${req.params.survey}.xlsx"`)
        return workbook.xlsx.write(res);
    }).then(() => {
        res.end();
    }).catch((e) => {
        res.status(404);
        res.send(e.message);
    });
});

app.listen(port, () => console.log(`Example app listening on port ${port}!`));