nodejs_email_oauth3.ts

// create reusable transporter object using the default SMTP transport
const transporter = nodemailer.createTransport({
    service: 'gmail',
    auth: {
        type: 'OAuth2',
        user: OAUTH_EMAIL,
        clientId: OAUTH_CLIENT_ID,
        clientSecret: OAUTH_CLIENT_SECRET,
        refreshToken: OAUTH_REFRESH_TOKEN,
        accessToken: accessToken.toString()
    }
});

// create mail options
const mailOptions = {
    from: OAUTH_EMAIL,
    to: 'someone@example.com',
    subject: 'Hello ✔',
    text: 'Hello world?',
};

// send mail
transporter.sendMail(mailOptions, (error, info) => {
    if (error) {
        return console.log(error);
    }
    console.log('Message sent: %s', info.messageId);
});