smtp.js

var client = nodemailer.createTransport({
  service: 'SendGrid',
  auth: {
    user: 'SENDGRID_USERNAME',
    pass: 'SENDGRID_PASSWORD'
  }
});

// See above

web.js

var nodemailer = require('nodemailer');
var sgTransport = require('nodemailer-sendgrid-transport');

var options = {
  auth: {
    api_user: 'SENDGRID_USERNAME',
    api_key: 'SENDGRID_PASSWORD'
  }
}

var client = nodemailer.createTransport(sgTransport(options));

var email = {
  from: 'awesome@bar.com',
  to: 'mr.walrus@foo.com',
  subject: 'Hello',
  text: 'Hello world',
  html: '<b>Hello world</b>'
};

client.sendMail(email, function(err, info){
    if (err ){
      console.log(error);
    }
    else {
      console.log('Message sent: ' + info.response);
    }
});

Would it be possible to use a SendGrid template instead of:

var email = { from: 'awesome@bar.com', to: 'mr.walrus@foo.com', subject: 'Hello', text: 'Hello world', html: '<b>Hello world</b>' };