index.js

/*
All the index.js code from first article 
*/

function getAuth(auth){
    var Mail = require('./createMail.js');
    var obj = new Mail(auth, "receiver's gmail Id", 'Subject', 'Body', 'mail');
    
    //'mail' is the task, if not passed it will save the message as draft.
    //attachmentSrc array is optional.
    obj.makeBody();
    //This will send the mail to the recipent.
}