JSMail is a JavaScript Library that lets you send emails in JavaScript!
You can hook into the library by doing...
<script src="http://jsmail.jacobgasser.com/mail.js"></script>
To send an email, simply use the send(); function.
<button onclick="send('Message', 'Subject', 'SendTo'">Send Email</button>
Where Message is your message you want to send, Subject is the subject of that message, and SendTo is the email address of that person.
You can also download mail.js inside of the JSLib folder.