Sendgrid v3 updated version

emailSender.js

// An example to use the Mailer.js Class
const mongoose = require('mongoose');
const Mailer = require('../services/Mailer');

const Survey = mongoose.model('surveys');

app.post('/api/surveys', (req, res) => {
        const { title, subject, body, recipients } = req.body;

        const survey = new Survey({
            title,
            body,
            subject,
            recipients: recipients
                .split(',')
                .map(email => ({ email: email.trim() })),
            _user: req.user.id,
            dateSent: Date.now(),
        });

        // Send an email here!
        const mailer = new Mailer(survey, `<div>${survey.body}</div>`);
        mailer.send();
    });

Mailer.js

const sgMail = require('@sendgrid/mail'); // separate Node package
const helpers = require('@sendgrid/helpers'); // separate Node package
const keys = require('../config/keys'); // some place where you store your API keys

class Mailer extends helpers.classes.Mail {
    // Through the use of Static methods from the Mail helper Class, you create a sendgrid compliant instance that can be send easily
    constructor({ subject, recipients }, content) {
        super();
        this.setFrom('no-reply@emaily.com'); // uses the EmailAddress.create method
        this.setSubject(subject);
        this.addHtmlContent(content); // same as addContent, but more specific for HTML

        this.recipients = recipients.map(({ email }) =>
            helpers.classes.EmailAddress.create(email)
        );

        this.setTrackingSettings({
            clickTracking: { enable: true, enableText: true },
        });

        this.addTo(this.recipients); // This uses the personalization method in the background
    }

    // To separate our data from what we send out, we create another function
    async send() {
        sgMail.setApiKey(keys.sendGridKey);

        return await sgMail.send(this); // attach the current instance to be send out with SendGrid
    }
}

module.exports = Mailer;