Skip to main content
Reply to messages that have been previously sent in the chat room. Message replies are implemented using the metadata field when you send a message.

​
Send a reply

Use the metadata field of a message to store the reply when you send a message. You need to at least include the serial of the parent message that you’re replying to. Other information can be included such as a preview of the text: 
async function sendReply(replyToMessage, replyText) {
  const metadata = {
    reply: {
      serial: replyToMessage.serial,
      timestamp: replyToMessage.timestamp.getTime(),
      clientId: replyToMessage.clientId,
      previewText: replyToMessage.text.substring(0, 140)
    }
  };

  await room.messages.send({
    text: replyText,
    metadata: metadata
  });
}
Ably achieves a global median message delivery latency of 37ms, ensuring replies appear instantly across all participants.

​
Subscribe to message replies

Message replies will be received as normal messages in the room using the subscribe() method. You just need to handle storing and displaying the reply.

​
Store reply information

When a user replies to a message, extract and store the parent message details: 
function prepareReply(parentMessage) {
  return {
    serial: parentMessage.serial,
    timestamp: parentMessage.timestamp.getTime(),
    clientId: parentMessage.clientId,
    previewText: parentMessage.text.substring(0, 140)
  };
}
If a parent message isn’t in local state, fetch it directly using its serial: 
async function fetchParentMessage(replyData) {
  const message = await room.messages.get(replyData.serial);
  return message;
}

​
Display replies

Check incoming messages for reply metadata and display accordingly: 
room.messages.subscribe((messageEvent) => {
  const message = messageEvent.message;

  if (message.metadata?.reply) {
    const replyData = message.metadata.reply;
    const parentMessage = localMessages.find(msg => msg.serial === replyData.serial);

    if (parentMessage) {
      console.log(`Reply to ${parentMessage.clientId}: ${parentMessage.text}`);
    } else {
      console.log(`Reply to ${replyData.clientId}: ${replyData.previewText}`);
    }
  }

  console.log(`Message: ${message.text}`);
});

​
Considerations

Consider the following when implementing message replies:
  • Older messages may not be available depending on message persistence settings.
  • Messages can be updated, potentially removing references to replies.
  • The metadata field is not server-validated.
  • Nested replies can be complex and expensive to implement, so consider limiting reply depth.

Build docs developers (and LLMs) love

Get started for freeTalk to us