Node.js — Scheduling Cron Jobs

3 min readFeb 25, 2023

Scheduling cron jobs can actually save you precious time & let you focus on other important tasks.

But what is cron job?

Cron Job is a command that is used to schedule jobs to be executed in the near future. For example, notifications every Monday at 12.00.

A Cron is a time-based job scheduler, which enables applications to schedule a job to run automatically at a certain date or time.

There are various open-source tools available for scheduling cron jobs in Node.js. In this article, we will look at a simple example using a module called node-cron.

Installing Dependencies

In this article, we would be creating a cron job to send emails. Create a simple Node.js project by running the following command in a terminal or bash.

mkdir node-cron-job-scheduler
cd node-cron-job-scheduler
npm init -y
touch index.js

Install the following dependencies.

npm install — save express node-cron nodemailer

In index.js file, import the above dependencies.

const cron = require(“node-cron”);
const express = require(“express”);
const nodeMailer = require(‘nodemailer’);

We will now create a simple Node server by adding:

app = express();
…
app.listen(8000);

Creating a Test Email Account

Before we create a cron job, let’s create a test email account at https://ethereal.email/. We will use these test credentials to send an email. We can also create test user account using nodemailer module as follows:

let testAccount = nodemailer.createTestAccount();

testAccount.user and testAccount.pass can be used for providing credentials to Mail transporter object.

`Scheduling Cron Job`

Let us create a cron job using node-cron module.

cron.schedule(“* * * * *”, function () {console.log(“Running Cron Job”);});

Here, the cron job runs for every minute. Start the Node.js server and you will see the message “Running Cron Job” in the console at every minute. We can schedule jobs at different days or time.

For example: “* * 5 * *“ => This represents 5th of every month. “30 7 * * *” represents every day at 7th hour and 30th minute.

Let’s add the logic to send email using nodemailer module within the cron job.

let transporter = nodeMailer.createTransport({
host: ‘smtp.ethereal.email’,
port: 587,
secure: false, // true for 465, false for other ports
auth: {
user: ‘<TEST_USER>’, // generated ethereal user
pass: ‘<TEST_PASSWORD>’ // generated ethereal password
}
});
const mailOptions = {
from: ‘“John Doe” <john.doe@example.com>’, // sender address
to: ‘jane.doe@example.com’, // list of receivers
subject: ‘Hello there!’, // Subject line
text: ‘A Message from Node Cron App’, // plain text body
html: ‘<b>A Message from Node Cron App</b>’ // html body
};
transporter.sendMail(mailOptions, function (error, info) {
console.log(info.messageId);
if (err) {
console.log(err);
}
});