Best Practices

Build reliable CometChat JavaScript SDK apps with secure auth, listener cleanup, pagination, caching, error handling, and performance practices.

Follow these best practices to build reliable, performant, and secure applications with the CometChat JavaScript SDK. Organized by topic — jump to what’s relevant for your current work.

Initialization & Authentication

Practice	Description
Initialize once at startup	Call CometChat.init() in your entry file (index.js, main.js, or App.js). It only needs to be called once per session.
Use environment variables	Store App ID, Region, and Auth Key in environment variables rather than hardcoding them.
Check for existing sessions	Before calling login(), use CometChat.getLoggedinUser() to check if a session already exists.
Use Auth Tokens in production	Auth Keys are for development only. Generate Auth Tokens server-side using the REST API.
Handle token expiry	Implement a mechanism to detect login failures due to expired tokens. Use the Login Listener to detect session changes.
Logout on sign-out	Always call CometChat.logout() when your user signs out to clear the SDK session and stop real-time events.

Listeners

Practice	Description
Use unique listener IDs	Use descriptive IDs like "MESSAGE_LISTENER_CHAT_SCREEN" to avoid accidental overwrites.
Register early, remove on cleanup	Register listeners after login(). Remove them when the component is destroyed to prevent memory leaks.
Keep callbacks lightweight	Avoid heavy processing inside listener callbacks. Dispatch events to your state management layer.
Use specific listeners	Only register the listener types you need. Don’t register a GroupListener if your page only handles messages.

Pagination & Caching

Practice	Description
Use reasonable limits	Set setLimit() to 30-50 for users, messages, and group members.
Reuse request objects	Call fetchNext()/fetchPrevious() on the same request instance. Creating a new object resets the cursor.
Cache frequently accessed data	Store user and group objects locally to reduce API calls.

Rate Limits

Practice	Description
Batch operations	Space out bulk operations using a queue or throttle mechanism.
Monitor rate limit headers	Check X-Rate-Limit-Remaining in REST API responses to slow down before hitting limits.
Distinguish operation types	Core operations (login, create/delete user) share a 10,000/min limit. Standard operations have 20,000/min. Avoid frequent login/logout cycles.

SSR Frameworks

Practice	Description
Initialize client-side only	CometChat requires browser APIs. Use dynamic imports or useEffect for Next.js, Nuxt, etc.
Use loading states	Show a loading indicator while the SDK initializes to prevent hydration mismatches.

Messaging

Practice	Description
Use appropriate message types	Choose text, media, or custom messages based on your content.
Add metadata for context	Use setMetadata() to attach location, device info, or other contextual data.
Handle errors gracefully	Always implement error callbacks to handle network issues or invalid parameters.
Validate file types	Before sending media messages, verify the file type matches the message type.
Hide deleted/blocked content	Use hideDeletedMessages(true) and hideMessagesFromBlockedUsers(true) for cleaner lists.

Threaded Messages

Practice	Description
Track active thread ID	Store the current thread’s parentMessageId to filter incoming messages.
Use hideReplies(true)	Exclude thread replies from main conversation to avoid clutter.
Show reply count	Display the number of replies on parent messages to indicate thread activity.

Reactions & Mentions

Practice	Description
Update UI optimistically	Show reactions immediately, then sync with server response.
Use correct mention format	Always use <@uid:UID> format for mentions in message text.
Highlight mentions in UI	Parse message text and style mentions differently.

Typing Indicators

Practice	Description
Debounce typing events	Don’t call startTyping() on every keystroke - debounce to ~300ms intervals.
Auto-stop typing	Call endTyping() after 3-5 seconds of inactivity or when the user sends a message.

Delivery & Read Receipts

Practice	Description
Mark as delivered on fetch	Call markAsDelivered() when messages are fetched and displayed.
Mark as read on view	Call markAsRead() when the user actually views/scrolls to a message.
Batch receipts	Mark the last message in a batch - all previous messages are automatically marked.

Groups

Practice	Description
Use meaningful GUIDs	Choose descriptive, unique GUIDs (e.g., "project-alpha-team").
Set group type carefully	Group type cannot be changed after creation. Choose between PUBLIC, PASSWORD, and PRIVATE.
Add members at creation	Use createGroupWithMembers() to add initial members in a single API call.
Check hasJoined before joining	Avoid unnecessary API calls by checking the group’s hasJoined property first.
Transfer ownership before leaving	Owners must transfer ownership to another member before they can leave.
Use joinedOnly(true)	Filter to joined groups when building sidebars or group lists.

Group Members

Practice	Description
Batch member additions	Add multiple members in a single addMembersToGroup() call.
Set appropriate scopes	Assign PARTICIPANT by default. Only use ADMIN or MODERATOR when needed.
Handle partial failures	Check each entry in the response array for "success" or an error message.
Use scope constants	Use CometChat.GROUP_MEMBER_SCOPE.ADMIN instead of raw strings.
Kick vs. Ban	Use kick when the user can rejoin. Use ban for permanent removal until unbanned.

Calling

Practice	Description
Initialize Calls SDK after Chat SDK	Always initialize Chat SDK (CometChat.init()) before Calls SDK (CometChatCalls.init()).
Store session ID immediately	Save the session ID from initiateCall() response - you’ll need it for accept, reject, cancel.
Handle all call states	Implement handlers for all listener events (accepted, rejected, cancelled, busy, ended).
Generate tokens just-in-time	Generate call tokens immediately before starting a session rather than caching them.
Clean up on session end	Always call CometChatCalls.endSession() in both onCallEnded and onCallEndButtonPressed callbacks.
Inform users about recording	Always notify participants when recording starts - this is often a legal requirement.

Custom CSS (Calling)

Practice	Description
Only use documented CSS classes	Undocumented internal classes may break with SDK updates.
Don’t resize the grid container	Only customize colors, borders, and visibility.
Test across modes	CSS changes may look different in DEFAULT, TILE, and SPOTLIGHT modes.
Keep button sizes accessible	Minimum 44x44px for touch targets.

Connection & WebSocket

Practice	Description
Register connection listener early	Add the listener right after CometChat.init() succeeds.
Show connection status in UI	Display a banner when disconnected so users know messages may be delayed.
Queue actions during disconnection	Queue user actions and retry once onConnected fires.
Don’t poll getConnectionStatus()	Use the listener-based approach instead.
Reconnect on app foreground	If you disconnect in background, call CometChat.connect() when returning to foreground.

AI Features

Practice	Description
Register both listeners for AI Agents	Use AIAssistantListener for streaming events and MessageListener for persisted messages.
Handle streaming progressively	Render the assistant’s reply token-by-token using Text Message Content events.
Show pending state for moderation	Display a visual indicator when getModerationStatus() returns PENDING.
Handle disapproved messages gracefully	Show a placeholder or notification so the sender understands what happened.
Track pending messages	Maintain a local map of pending message IDs to update UI when moderation results arrive.

Upgrading from V3

Practice	Description
Follow the setup guide first	Complete the v4 setup instructions before changing imports.
Update all imports at once	Use find-and-replace to change all @cometchat-pro/chat imports to @cometchat/chat-sdk-javascript.
Test incrementally	Test each feature area (messaging, calling, groups) individually after updating.
Remove old packages	Uninstall v3 packages (npm uninstall @cometchat-pro/chat) to avoid conflicts.

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Next Steps

Troubleshooting

Common issues and solutions

Error Codes

Complete SDK error code reference

Rate Limits

Understand and handle API rate limits

Setup SDK

Installation and initialization guide