How to Run Cron Jobs in Node.js ?

Last Updated : 17 Oct, 2024

Cron jobs are scheduled tasks that run at specific intervals in the background, commonly used for maintenance or repetitive tasks. Users can schedule commands the OS will run these commands automatically according to the given time. It is usually used for system admin jobs such as backups, logging, sending newsletters, subscription emails and more.

Prerequisites:

Node.js installed
NPM installed

To run the cron-jobs in Node.js we will be using the node-cron library. Install and import it into your project. You then define a cron expression that determines the task's schedule and use cron.schedule() to execute functions at specified intervals.

Syntax:

cron.schedule("* * * * *", function() {
    // Task to do
});

Steps to Create Node App

Step 1: Go to the project directory and run this command in the terminal

npm init -y

Step 2: Install the required Modules

npm install express node-cron

The updated dependencies in the package.json are:

"dependencies": {
    "express": "^4.18.2",
    "node-cron": "^3.0.0"
}

Time formatting for Cron jobs

Descriptors with their ranges

Seconds (optional): 0 - 59
Minute: 0 - 59
Hour: 0 - 23
Day of the Month: 1 - 31
Month: 1 - 12
Day of the week: 0 - 7 (0 and 7 both represent Sunday)

Examples:

(*/10 * * * *) - Runs on every 10 minutes
(* * 21 * *) - Runs 21^th of every month
(0 8 * * 1) - Runs 8 AM on every Monday

Example: Create a new file named index.js and add the following code:

JavaScript

// Importing required libraries
const cron = require("node-cron");
const express = require("express");

app = express(); // Initializing app

// Creating a cron job which runs on every 10 second
cron.schedule("*/10 * * * * *", function() {
    console.log("running a task every 10 second");
});

app.listen(3000);

Run the file using command

node index

, you will see the output like below:

Writing to a log file

ron jobs can be used to schedule logging tasks in a system. We can log server status for a given time for monitoring purposes.

Example: This example sets up a cron job using node-cron to log a status message to logs.txt every 10 seconds.

JavaScript

// index.js
// Importing required packages
const cron = require("node-cron");
const express = require("express");
const fs = require("fs");

app = express();

// Setting a cron job
cron.schedule("*/10 * * * * *", function() {

    // Data to write on file
    let data = `${new Date().toUTCString()} 
                : Server is working\n`;
    
    // Appending data to logs.txt file
    fs.appendFile("logs.txt", data, function(err) {
        
        if (err) throw err;
        
        console.log("Status Logged!");
    });
});

app.listen(3000);

After running above file for 30-40 seconds, you will see a file created named logs.txt having content somewhat similar to the following:

Monthly Newsletters

Sending monthly newsletters are also a use case for cron jobs in which an email will be sent to the users monthly with the latest products or blog information on the website. You can learn more about sending email in Node.js here.

Example: This example uses node-cron to send an email every minute with Nodemailer, automatically triggering the sendMail() function.

JavaScript

// index.js
// Importing packages
const cron = require("node-cron");
const express = require("express");
const nodemailer = require("nodemailer");

app = express();

// Calling sendEmail() function every 1 minute
cron.schedule("*/1 * * * *", function() {
sendMail();
});

// Send Mail function using Nodemailer
function sendMail() {
    let mailTransporter = nodemailer.createTransport({
        service: "gmail",
        auth: {
        user: "<your-email>@gmail.com",
        pass: "**********"
        }
    });
    
    // Setting credentials
    let mailDetails = {
        from: "<your-email>@gmail.com",
        to: "<user-email>@gmail.com",
        subject: "Test mail using Cron job",
        text: "Node.js cron job email"
           + " testing for GeeksforGeeks"
    };
    
    
    // Sending Email
    mailTransporter.sendMail(mailDetails, 
                    function(err, data) {
        if (err) {
            console.log("Error Occurs", err);
        } else {
            console.log("Email sent successfully");
        }
    });
}

app.listen(3000);