+```javascript
+import { Message } from '@ably/chat';
+function prepareReply(parentMessage: Message) {
+ // Extract key information from the parent message
+ const replyingTo = {
+ serial: parentMessage.serial,
+ createdAt: parentMessage.createdAt.getTime(),
+ clientId: parentMessage.clientId,
+ previewText: parentMessage.text.length > 140
+ ? parentMessage.text.substring(0, 137) + '...'
+ : parentMessage.text
+ };
+ return replyingTo;
+}
+```
+
+```react
+import React from 'react';
+import { Message } from '@ably/chat';
+
+// In a React component
+const ChatComponent = () => {
+ const [replyingTo, setReplyingTo] = React.useState();
+ // Function to prepare reply data
+ const prepareReply = (parentMessage) => {
+ // Extract key information from the parent message
+ const replyingTo = {
+ serial: parentMessage.serial,
+ createdAt: parentMessage.createdAt.getTime(),
+ clientId: parentMessage.clientId,
+ previewText: parentMessage.text.length > 140
+ ? parentMessage.text.substring(0, 137) + '...'
+ : parentMessage.text
+ };
+
+ // Store in component state
+ setReplyingTo(replyingTo);
+ };
+
+ // Example usage with a button
+ return (
+
+ {/* Message display */}
+
+ {/* Message content */}
+
+
+
+ );
+};
+```
+
+
+### Send a reply message with metadata
+
+When sending a reply message, include the parent message's information in the metadata.
+Create a metadata object with a property that contains the parent message's serial, timestamp and optionally the clientId and a snippet of the parent text (for previewing).
+
+The structure of your metadata could look like this:
+
+
+```json
+{
+ "reply": {
+ "serial": "parent-message-serial",
+ "createdAt": 1634567890123,
+ "clientId": "sender-id",
+ "previewText": "Snippet of the parent message..."
+ }
+};
+```
+
+
+
+```javascript
+import { Message } from '@ably/chat';
+
+async function sendReply(replyToMessage: Message, replyText: string) {
+ try {
+ // Create metadata object with reply information
+ const metadata = {
+ reply: {
+ serial: replyToMessage.serial,
+ timestamp: replyToMessage.createdAt.getTime(),
+ clientId: replyToMessage.clientId,
+ previewText: replyToMessage.text.length > 140
+ ? replyToMessage.text.substring(0, 140) + '...'
+ : replyToMessage.text
+ }
+ };
+
+ // Send the message with reply metadata
+ const message = await room.messages.send({
+ text: replyText,
+ metadata: metadata
+ });
+
+ console.log('Reply sent successfully:', message);
+ return message;
+ } catch (error) {
+ console.error('Failed to send reply:', error);
+ throw error;
+ }
+}
+
+// Example usage
+const replyText = "I'm responding to your message!";
+
+await sendReply(messageToReplyTo, replyText);
+```
+
+```react
+import React, { useState } from 'react';
+import { useMessages } from '@ably/chat/react';
+
+const ReplyComponent = ({ messageToReplyTo }) => {
+ const [replyText, setReplyText] = useState('');
+ const { sendMessage } = useMessages();
+
+ const sendReply = async () => {
+ try {
+ // Create metadata object with reply information
+ const metadata = {
+ reply: {
+ serial: messageToReplyTo.serial,
+ createdAt: messageToReplyTo.createdAt.getTime(),
+ clientId: messageToReplyTo.clientId,
+ previewText: messageToReplyTo.text.length > 140
+ ? messageToReplyTo.text.substring(0, 140) + '...'
+ : messageToReplyTo.text
+ }
+ };
+
+ // Send the message with reply metadata
+ await sendMessage({
+ text: replyText,
+ metadata: metadata
+ });
+
+ // Clear input after sending
+ setReplyText('');
+
+ console.log('Reply sent successfully');
+ } catch (error) {
+ console.error('Failed to send reply:', error);
+ }
+ };
+
+ return (
+
+ Replying to: {messageToReplyTo.clientId}
+ {messageToReplyTo.text}
+ setReplyText(e.target.value)}
+ placeholder="Type your reply..."
+ />
+
+
+ );
+};
+```
+
+
+
+ ```javascript
+ const parentMessage = await room.messages.send({
+ text: "Hello, this is the parent message!"
+});
+
+ const replyText = "This is a reply to the parent message!";
+
+ await sendReply(parentMessage, replyText);
+ ```
+
+
+```javascript
+// Subscribe to messages and handle replies
+const messageSubscription = room.messages.subscribe((messageEvent) => {
+ const message = messageEvent.message;
+
+ // Check if this is a reply message
+ if (message.metadata && message.metadata.reply) {
+ const replyData = message.metadata.reply;
+
+ // Find the parent message in your local state
+ const parentMessage = localMessages.find(msg => msg.serial === replyData.serial);
+
+ // Display the reply message
+ displayReply(message, parentMessage, replyData);
+ }
+});
+
+function displayReply(replyMessage, parentMessage, replyData) {
+ if (parentMessage) {
+ console.log(`Reply from ${replyMessage.clientId} to ${parentMessage.clientId}'s message: "${parentMessage.text}"`);
+ } else {
+ console.log(`Reply from ${replyMessage.clientId} to a message by ${replyData.clientId}`);
+ }
+ console.log(`Reply text: ${replyMessage.text}`);
+}
+```
+
+```react
+import React, { useState, useEffect } from 'react';
+import { useMessages } from '@ably/chat/react';
+import { ChatMessageEventType, Message } from '@ably/chat';
+
+const MessageList = () => {
+ const [messages, setMessages] = useState {
+ if (event.type === ChatMessageEventType.Created) {
+ setMessages(prev => [...prev, event.message]);
+ }
+ }
+ });
+
+ // Find the parent message for a reply
+ const findParentMessage = (replyData) => {
+ return messages.find(msg => msg.serial === replyData.serial);
+ };
+
+ // Render messages with reply context
+ return (
+
+ {messages.map(message => (
+
+ {message.metadata?.reply && (
+
+ {findParentMessage(message.metadata.reply) ? (
+
+ Replying to {findParentMessage(message.metadata.reply).clientId}:
+ {findParentMessage(message.metadata.reply).text}
+
+ ) : (
+
+ Replying to {message.metadata.reply.clientId}:
+ {message.metadata.reply.previewText}
+
+ )}
+
+ )}
+
+
+ {message.clientId}
+ {message.createdAt.toLocaleTimeString()}
+
+ {message.text}
+
+
+ ))}
+
+ );
+};
+```
+
+
+Your message subscription logic should check for the reply metadata and handle it appropriately.
+
+When displaying a reply message, you might want to show a preview of the parent message, the name of the its sender, or a visual indication that it's a reply.
+
+## Find parent messages that aren't in local state
+
+If a reply references a message that isn't in your local state (for example, if a user just joined the chat), you can use the history methods to find it. Here's how:
+
+1. Extract the serial and createdAt from the reply metadata.
+2. Use the exact createdAt time from the metadata to query messages, as start and end params are inclusive.
+3. Use the
+```javascript
+// Function to fetch the parent message referenced in a reply
+async function fetchParentMessage(replyData) {
+ const timestamp = replyData.createdAt;
+ try {
+ // Query messages at this specific timestamp
+ let result = await room.messages.history({
+ start: timestamp,
+ end: timestamp,
+ limit: 20
+ });
+
+ // Find the message with the matching serial
+ let parentMessage = result.items.find(msg => msg.serial === replyData.serial);
+
+ // If the message is not found and more pages exist, continue searching
+ while (!parentMessage && result.hasNext()) {
+ // Get the next page of results
+ result = await result.next();
+ parentMessage = result.items.find(msg => msg.serial === replyData.serial);
+ }
+ return parentMessage;
+ } catch (error) {
+ console.error('Error fetching parent message:', error);
+ // Handle error appropriately in your application
+ }
+}
+```
+
+```react
+import React, { useState, useEffect } from 'react';
+import { useMessages } from '@ably/chat/react';
+import { Message } from '@ably/chat';
+
+const FetchParentMessage = ({ replyData }) => {
+ const [parentMessage, setParentMessage] = useState();
+ const { history } = useMessages();
+
+ useEffect(() => {
+ const fetchMessage = async () => {
+ try {
+ // Query messages at the specific timestamp
+ let result = await history({
+ start: replyData.createdAt,
+ end: replyData.createdAt,
+ limit: 20
+ });
+
+ // Find the message with the matching serial
+ let foundMessage = result.items.find(
+ msg => msg.serial === replyData.serial
+ );
+
+ // If the message is not found and more pages exist, continue searching
+ while (!foundMessage && result.hasNext()) {
+ // Get the next page of results
+ result = await result.next();
+ foundMessage = result.items.find(msg => msg.serial === replyData.serial);
+ }
+ // Set the parent message in state
+ setParentMessage(foundMessage);
+
+ } catch (err) {
+ console.error('Error fetching parent message:', err);
+ }
+ };
+
+ fetchMessage();
+ }, [history, replyData]);
+
+
+ return (
+
+ {parentMessage && (
+
+ Parent Message:
+ {parentMessage.text}
+ Sent by: {parentMessage.clientId}
+
+ )}
+
+ );
+};
+```
+
+
+Here the exact timestamp is used to narrow down the search, reducing the number of messages to check. Since the start and end parameters are inclusive, you can set both to the exact timestamp of the parent message.
+
+If many messages are sent around the same time, you might want to increase the limit or handle pagination to ensure you find the parent message.
+
+## Use historyBeforeSubscribe
+
+The [`historyBeforeSubscribe`](https://sdk.ably.com/builds/ably/ably-chat-js/main/typedoc/interfaces/chat-js.SubscribeMessagesResponse.html#historyBeforeSubscribe) method is another option that can be used to query history. It allows you to search backwards from the point you attach to a room, which can be useful for finding parent messages for recent replies.
+
+The bonus here is that it will only return messages that were sent before you subscribed, and you get to backfill your local state at the same time. While this is useful for recent messages, it may not be the best option for older messages or high message rate situations.
+
+As such, its important to define a reasonable threshold for how far back you want to search in this way. This can help avoid performance issues and unnecessary data retrieval.
+- A good default might be to go backwards up to a week or N messages.
+- If you find a reply whos parent message is beyond your threshold, you can choose to page further, or load these on a case by case basis via the `history` function.
+
+For most cases, using the `history` function to load only the specific message you care about, as shown in the previous section, is the recommended approach.
+
+## Example
+
+
+```javascript
+import { Realtime } from 'ably';
+import { ChatClient, ChatMessageEventType } from '@ably/chat';
+
+const messages = [];
+let replyingTo = null;
+
+// Find parent message for a reply
+function findParentMessage(serial) {
+ return messages.find(msg => msg.serial === serial) || null;
+}
+
+// Set up replying to a message
+function prepareReply(message) {
+ replyingTo = {
+ serial: message.serial,
+ createdAt: message.createdAt.getTime(),
+ clientId: message.clientId,
+ previewText: message.text.length > 100
+ ? message.text.substring(0, 100) + '...'
+ : message.text
+ };
+
+ // Update UI to show reply preview
+ showReplyPreview(replyingTo);
+}
+
+// Send a message with optional reply metadata
+async function sendMessage(room, text) {
+ if (!text.trim()) return;
+
+ const messageParams = { text };
+
+ if (replyingTo) {
+ messageParams.metadata = {
+ reply: {
+ serial: replyingTo.serial,
+ createdAt: replyingTo.createdAt,
+ clientId: replyingTo.clientId,
+ previewText: replyingTo.previewText
+ }
+ };
+
+ // Clear reply state after sending
+ replyingTo = null;
+ hideReplyPreview();
+ }
+
+ await room.messages.send(messageParams);
+}
+
+function renderMessage(message) {
+ const messageEl = document.createElement('div');
+ messageEl.className = 'message';
+
+ // Add reply context if this is a reply
+ if (message.metadata?.reply) {
+ const replyData = message.metadata.reply;
+ const parentMessage = findParentMessage(replyData.serial);
+
+ const replyContext = document.createElement('div');
+ replyContext.className = 'reply-context';
+
+ if (parentMessage) {
+ replyContext.textContent = `Replying to ${parentMessage.clientId}: ${parentMessage.text}`;
+ } else {
+ replyContext.textContent = `Replying to ${replyData.clientId}: ${replyData.previewText}`;
+ }
+
+ messageEl.appendChild(replyContext);
+ }
+
+ // Add message content
+ const content = document.createElement('div');
+ content.textContent = `${message.clientId}: ${message.text}`;
+ messageEl.appendChild(content);
+
+ // Add reply button
+ const replyButton = document.createElement('button');
+ replyButton.textContent = 'Reply';
+ replyButton.onclick = () => prepareReply(message);
+ messageEl.appendChild(replyButton);
+
+ // Add to container
+ document.getElementById('message-container').appendChild(messageEl);
+}
+
+function showReplyPreview(replyData) {
+ const previewEl = document.getElementById('reply-preview');
+ previewEl.innerHTML = `
+ Replying to ${replyData.clientId}: ${replyData.previewText}
+ `;
+ previewEl.style.display = 'block';
+}
+
+function hideReplyPreview() {
+ replyingTo = null;
+ document.getElementById('reply-preview').style.display = 'none';
+}
+
+// Initialize the chat when the page loads
+document.addEventListener('DOMContentLoaded', async () => {
+ try {
+ const apiKey = '{{API_KEY}}'; // Replace with your actual API key
+ const clientId = 'user-' + Math.floor(Math.random() * 1000);
+ const roomName = 'chat-room';
+
+ const client = new Realtime({ key: apiKey, clientId });
+ const chatClient = new ChatClient(client);
+ const room = await chatClient.rooms.get(roomName);
+
+ // Subscribe to new messages
+ room.messages.subscribe((event) => {
+ console.log('New message:', event);
+ if (event.type === ChatMessageEventType.Created) {
+ messages.push(event.message);
+ renderMessage(event.message);
+ }
+ });
+ await room.attach()
+
+ // Set up send button click handler
+ document.getElementById('send-button').onclick = () => {
+ const inputEl = document.getElementById('message-input');
+ sendMessage(room, inputEl.value);
+ inputEl.value = '';
+ };
+
+ // Also allow sending with Enter key
+ document.getElementById('message-input').addEventListener('keypress', (e) => {
+ if (e.key === 'Enter') {
+ const inputEl = document.getElementById('message-input');
+ sendMessage(room, inputEl.value);
+ inputEl.value = '';
+ }
+ });
+
+ console.log('Chat initialized successfully!');
+ } catch (error) {
+ console.error('Error initializing chat:', error);
+ document.getElementById('message-container').innerHTML =
+ ``;
+ }
+});
+```
+
+```react
+import React, { useState, useEffect } from 'react';
+import { useMessages } from '@ably/chat/react';
+import { Message, ChatMessageEventType } from '@ably/chat';
+
+const ChatComponent = () => {
+ const [messages, setMessages] = useState([]);
+ const [inputText, setInputText] = useState('');
+ const [replyingTo, setReplyingTo] = useState(null);
+
+ const { sendMessage } = useMessages({
+ listener: (event) => {
+ if (event.type === ChatMessageEventType.Created) {
+ setMessages(prev => [...prev, event.message]);
+ }
+ }
+ });
+
+ const handleSend = async () => {
+ if (!inputText.trim()) return;
+
+ try {
+ if (replyingTo) {
+ const metadata = {
+ reply: {
+ serial: replyingTo.serial,
+ createdAt: replyingTo.createdAt.getTime(),
+ clientId: replyingTo.clientId,
+ previewText: replyingTo.text.length > 140
+ ? replyingTo.text.substring(0, 137) + '...'
+ : replyingTo.text
+ }
+ };
+ await sendMessage({ text: inputText, metadata });
+ setReplyingTo(null);
+ } else {
+ await sendMessage({ text: inputText });
+ }
+ setInputText('');
+ } catch (error) {
+ console.error('Failed to send message:', error);
+ }
+ };
+
+ // Find parent message for a reply
+ const findParentMessage = (serial) => {
+ return messages.find(msg => msg.serial === serial);
+ };
+
+ return (
+
+ {/* Message list */}
+
+ {messages.map((message) => (
+
+ {/* Reply context */}
+ {message.metadata?.reply && (
+
+ {(() => {
+ const parent = findParentMessage(message.metadata.reply.serial);
+ if (parent) {
+ return `Replying to ${parent.clientId}: ${parent.text}`;
+ } else {
+ return `Replying to ${message.metadata.reply.clientId}: ${message.metadata.reply.previewText}`;
+ }
+ })()}
+
+ )}
+
+ {/* Message content */}
+
+ {message.clientId}: {message.text}
+
+
+ {/* Reply button */}
+
+
+ ))}
+
+
+ {/* Reply preview */}
+ {replyingTo && (
+
+
+ Replying to {replyingTo.clientId}: {replyingTo.text.length > 50
+ ? replyingTo.text.substring(0, 47) + '...'
+ : replyingTo.text}
+
+
+
+ )}
+
+ {/* Message input */}
+
+ setInputText(e.target.value)}
+ placeholder="Type a message..."
+ style={{
+ flex: 1,
+ padding: '8px',
+ border: '1px solid #ccc',
+ borderRadius: '4px'
+ }}
+ />
+
+
+
+ );
+};
+
+```
+
+
+The steps outlined in the previous sections provide the foundation for building a complete reply system in your application.
+
+## Limitations and considerations
+
+When implementing replies and quotes using metadata, keep these considerations in mind:
+
+1. **Message availability**: If a quoted message is very old, it might not be available in history anymore, depending on your Ably account's [message persistence](docs/storage-history/storage#persist-last-message) settings.
+
+2. **Message updates**: Because messages can be updated (including the metadata), it's possible to accidentally remove the quoted message reference. Also, if providing a message preview, you will have to handle updates to the parent message text, as the preview might become outdated.
+
+3. **No server-side validation**: Since metadata is not validated by the server, you should ensure that your application logic correctly handles cases where the metadata might be malformed or missing.
+
+4. **Local state management**: Maintaining a local state of messages will improve performance by reducing the need to query history.
+
+5. **Tracking replies**: There isn't an easy way to know if a message has been replied to, other than to see its replies in history.
+
+6. **Nested replies**: Implementing nested replies (replies to replies) in this fashion can be potentially expensive and error-prone. You may have to query history multiple times to fetch all nested replies, and either:
+ - Store the reply metadata for all of a child's parents in its own metadata field, or
+ - Do a new history fetch for each message as you make your way up the reply tree.
+
+## Next steps
+
+* Explore the [Ably Chat documentation](/docs/chat) for API details.
+* Play around with the [Ably Chat examples](/examples?product=chat).
+* Try out the [livestream chat demo](https://ably-livestream-chat-demo.vercel.app).
+* Read the [JavaScript / TypeScript](/docs/chat/getting-started/javascript) or [React](/docs/chat/getting-started/react) getting started guides.
+
+For more information on working with Ably Chat, refer to:
+* [Messages](/docs/chat/rooms/messages?lang=javascript)
+* [Message history](/docs/chat/rooms/history?lang=javascript)
+* [Setup](/docs/chat/setup?lang=javascript)