Build an Email Scheduler with Express, Vue, Nodemailer, Node-cron and MongoDB

4 min readApr 7, 2023

Hi,

This article covers sending emails in a Node JS application. If you want to send a simple email with attached docs, this article covers it

Here are some simple steps to follow for that:

This is the project structure of the application

Step #1: Install the module needed for the project in your app

To do so, we need to use a package manager, either NPM or Yarn as you want:

npm install nodemailer body-parser cors node-cron express dotenv mutler

Step #2: Add this in your server.js file

const express = require("express");
const bodyParser = require("body-parser");
const cors = require("cors");
const dotenv = require("dotenv");

const PORT = process.env.PORT || 3000;
dotenv.config();

const app = express();
const router = express.Router();
const cronsRoutes = require("./routes/cron");

app.use(morgan("combined"));
app.use(bodyParser.json());
app.use(cors());
app.use("/api", cronsRoutes);
app.listen(PORT, () => console.log(`Listening on ${PORT}`));
app.get("/h", (req, res) => {
  res.send("Successful response.");
});
app.use("/", router);

in this file all we did was to import all the files / dependencies we’ll be using for the application

Step #3: we’ll be using multer for file upload Add this in your upload-file.js in middlewares folder

const multer = require("multer");

var Storage = multer.diskStorage({
    destination: function (req, file, callback) {
        callback(null, './images')
    },
    filename: function (req, file, callback) {
        callback(null, file.fieldname + "_" + Date.now() + "_" + file.originalname)
    }
})
var upload = multer({
    storage: Storage
}).single('file')
module.exports = upload;

here we created a storage path in which the uploaded images would be stored

Step #4: Create a .env file at the root of your folder and add this


GOOGLE_APP_EMAIL=
GOOGLE_APP_PW=

in order to use gmail for sending mail you need to create a temporary password which is an app password ,in order to get the app password you’ll need to enable 2 step verification on your google account

Step #5: Add this in your cron.js in routes folder

before adding the file lets take a look at cron functions

there are 6 options which one can use in scheduling

cron.schedule('* * * * * *', () => {
   console.log("runs in every second")
});

# ┌────────────── second (optional)
 # │ ┌──────────── minute
 # │ │ ┌────────── hour
 # │ │ │ ┌──────── day of month
 # │ │ │ │ ┌────── month
 # │ │ │ │ │ ┌──── day of week
 # │ │ │ │ │ │
 # │ │ │ │ │ │
 # * * * * * *

now add this is your cron.js file…. in this file we require the dependencies we’ll be using…event emitter is use to emit event each time a function has been called



const cronJob = require('node-cron');
const express = require("express");
const router = express.Router();
const nodemailer = require('nodemailer');
const EventEmitter = require('events');
const emitter = new EventEmitter()
emitter.setMaxListeners(0)
const upload = require("../middlewares/upload-file");
const event = new EventEmitter();

// create an instance to send a mail
let mailTransporter = nodemailer.createTransport({
    service: "gmail",
    auth: {user: process.env.GOOGLE_APP_EMAIL,
        pass: process.env.GOOGLE_APP_PW
    }
});
// make a post request
router.post(`/crons`, async (req, res) => {
    upload(req, res, function (err) {
        try {
            // data that would be sent
            const data = {
                to: req.body.to,
                subject: req.body.subject,
                second: req.body.second,
                minute: req.body.minute,
                hour: req.body.hour,
                day: req.body.day,
                month: req.body.month,
                week: req.body.week,
                html: req.body.html,
                attachments: [{
                    path: req.file.path
                }]
            };
            console.log(data.minute, data.hour, data.day, data.month, data.week)
            //create a scheduler using node-cron each cron option we need to Use template literal back ticks and dollar sign to pass in the variable
            const task = cronJob.schedule(`*/${data.minute} ${data.hour} ${data.day} ${data.month} ${data.week}`, () => {
                // collect the data and send an email
                mailTransporter.sendMail(data, err => {
                    if (err) {
                        console.log(err)
                    } else {
                        res.json({
                            status: true,
                            message: "email sent",
                        });
                        console.log("email sent");
                        event.emit('JOB COMPLETED');
                    }

                });
            })
            event.on('JOB COMPLETED', () => {
                // stop task immeditely an email, has been sent
                task.stop();
            });

        } catch (error) {
        }
    })
});
module.exports = router;