title: Node.js change HTML code with a callback function
body: <p>I want to display a confirm message using HTML once I have sent an email via nodemailer. I am fairly new to node so I'm not sure if I'm missing something obvious.</p>
  
  <pre><code>app.post("/bye", function(req, res){
    // send e-mail
    var transporter = nodemailer.createTransport({
        ...
    });
  
    var mailOptions = {
        ...
    }
  
    transporter.sendMail(mailOptions, function(error, info){
        if(error){
            return console.log(error);
        }
        console.log('Message sent: ' + info.response);
  
        ... (Something here that is going to print a confirmation message  to the html code of the page)
    });
  
    res.end("yes");
  });
  </code></pre>
  
  <p>Thanks</p>