Class GmailDraft

var draft = GmailApp.getDrafts()[0]; // The first draft message in the drafts folder
draft.deleteDraft();
draft.getMessage(); // Throws exception.

var draft = GmailApp.getDrafts()[0]; // The first draft message in the drafts folder
var draftId = draft.getId();
var draftById = GmailApp.getDraft(draftId);
Logger.log(draft.getMessage().getSubject() == draftById.getMessage().getSubject());

var draft = GmailApp.getDrafts()[0]; // The first draft message in the drafts folder
var message = draft.getMessage();
Logger.log(message.getSubject());

var draft = GmailApp.getDrafts()[0]; // The first draft message in the drafts folder
var messageId = draft.getMessageId();
Logger.log(messageId == draft.getMessage().getId());

var draft = GmailApp.getDrafts()[0]; // The first draft message in the drafts folder
var msg = draft.send(); // Send it
Logger.log(msg.getDate()); // Should be approximately the current timestamp

// The code below will update a draft email with the current date and time.
var draft = GmailApp.getDrafts()[0]; // The first draft message in the drafts folder
var now = new Date();
draft.update("mike@example.com", "current time", "The time is: " + now.toString());

// Update a draft email with a file from Google Drive attached as a PDF.
var draft = GmailApp.getDrafts()[0]; // The first draft message in the drafts folder
var file = DriveApp.getFileById('1234567890abcdefghijklmnopqrstuvwxyz');
draft.update('mike@example.com', 'Attachment example', 'Please see attached file.', {
    attachments: [file.getAs(MimeType.PDF)],
    name: 'Automatic Emailer Script'
});