Class GmailDraft

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

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

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

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

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