This is a code snippet that you could use to send dynamic emails to your clients in NodeJS using NodeMailer.

sendEmail.js

import fs from 'fs';
import nodemailer from 'nodemailer';

async function sendEmail(data) {
    try {
        //destructure
        const { dataToReplace, emailSubject, recipientEmail } = data;

        // Replace with the actual path to your template file
        const templatePath = `./templates/loginTemplate`;

        // Read the template file
        let templateContent = fs.readFileSync(templatePath, 'utf8');

        // Replace placeholders with actual values
        Object.entries(dataToReplace).forEach(([placeholder, value]) => {
            const regex = new RegExp(`{{${placeholder}}}`, 'g');
            templateContent = templateContent.replace(regex, value);
        });

        const transporter = nodemailer.createTransport({
            host: 'MailingHost@server.com',
            port: 465,
            auth: {
                user: 'user@domain.com',
                pass: 'passForUser@domain.com'
            }
        });

        const mailOptions = {
            from: 'user@domain.com',
            replyTo: 'user@domain.com',
            to: recipientEmail,
            subject: emailSubject,
            html: templateContent
        };

        //send the email
        const info = await transporter.sendMail(mailOptions);
        //return response
        return info.response;
    } catch (error) {
        console.log(error);
    }
}

//construct the payload object
const emailPayload = {
    dataToReplace: {
        username: 'Octagon',
        ipAddress: '127.0.0.1',
        location: 'Lagos, Nigeria'
    },
    emailSubject: 'Account Login Notification',
    recipientEmail: 'test@tester.com'
}

//handle Promise with .then
sendEmail(emailPayload)
.then((res) => console.log(res))
.catch((err) => console.log(err))

//or use await
await sendEmail(emailPayload)