Class GmailThread

// Add label MyLabel to the first thread in the inbox
const label = GmailApp.getUserLabelByName('MyLabel');
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.addLabel(label);

// Create a draft reply to the message author with an acknowledgement.
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.createDraftReply('Got your message');

// Create a draft response with an HTML text body.
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.createDraftReply('incapable of HTML', {
  htmlBody: '<b>some HTML body text</b>',
  cc: 'another@example.com',
});

// Create a draft reply to all recipients (except those bcc'd) of the last email
// in this thread.
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
const message = firstThread.getMessages()[0];
message.createDraftReplyAll('Got your message');

// Create a draft reply, using an HTML text body, to all recipients (except
// those bcc'd) of the last email of in this thread.
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.createDraftReplyAll('incapable of HTML', {
  htmlBody: '<b>some HTML body text</b>',
  cc: 'another@example.com',
});

// Log the subject of the first message in the first thread in the inbox
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(firstThread.getFirstMessageSubject());

// Log the subject of the first message in the first thread in the inbox.
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
const id = firstThread.getId();
// Get same thread by its ID.
const thread = GmailApp.getThreadById(id);
Logger.log(
    thread.getFirstMessageSubject() === firstThread.getFirstMessageSubject(),
);  // True

// Log the names of the labels attached to the first thread in the inbox
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
const labels = firstThread.getLabels();
for (let i = 0; i < labels.length; i++) {
  Logger.log(labels[i].getName());
}

// Log the date of the most recent message on the first thread in the inbox
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(firstThread.getLastMessageDate());

// Log the number of messages in the thread
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(firstThread.getMessageCount());

// Log the subjects of the messages in the thread
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
const messages = firstThread.getMessages();
for (let i = 0; i < messages.length; i++) {
  Logger.log(messages[i].getSubject());
}

// Logs the permalink for the first thread in the inbox
const thread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(thread.getPermalink());

// Log if this thread has starred messages
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(`has starred : ${firstThread.hasStarredMessages()}`);

// Log if this thread is marked as important
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(`Important? : ${firstThread.isImportant()}`);

// Log if this thread is a chat
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(`is in chats? : ${firstThread.isInChats()}`);

// Log if this thread is in the inbox
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(`is in the inbox? : ${firstThread.isInInbox()}`);

// Log if this thread is in the priority inbox
const firstThread = GmailApp.getPriorityInboxThreads(0, 1)[0];
Logger.log(`is in priority inbox? ${firstThread.isInPriorityInbox()}`);

// Log if this thread is in the spam folder
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(`Spam? ${firstThread.isInSpam()}`);

// Log if this thread is in the trash
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(`Trashed? ${firstThread.isInTrash()}`);

// Log if this thread is unread
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
Logger.log(`Unread? ${firstThread.isUnread()}`);

// Mark first inbox thread as important
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.markImportant();

// Mark first inbox thread as read
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.markRead();

// Mark first inbox thread as unimportant
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.markUnimportant();

// Mark first inbox thread as unread
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.markUnread();

// Archive first inbox thread
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.moveToArchive();

// Move first non-inbox thread to inbox
const firstThread = GmailApp.search('-in:inbox')[0];
firstThread.moveToInbox();

// Move first inbox thread to spam
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.moveToSpam();

// Move first inbox thread to trash
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.moveToTrash();

const firstThread = GmailApp.getInboxThreads(0, 1)[0];
// ...Do something that may take a while here....
firstThread.refresh();  // Make sure it's up-to-date
// ...Do more stuff with firstThread ...

const myLabel = GmailApp.getUserLabelByName('<your label>');
const threads = myLabel.getThreads();
for (const thread of threads) {
  thread.removeLabel(myLabel);
}

// Respond to author of last email in thread with acknowledgment
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.reply('Got your message');

// Respond with HTML body text.
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.reply('incapable of HTML', {
  htmlBody: 'some HTML body text',
  noReply: true,
});

// Respond to all with acknowledgment to the first thread in the inbox
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.replyAll('Got your message');

// Respond with HTML body text.
const firstThread = GmailApp.getInboxThreads(0, 1)[0];
firstThread.replyAll('incapable of HTML', {
  htmlBody: 'some HTML body text',
  noReply: true,
});