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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.
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.
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
