diff --git a/index.js b/index.ts
similarity index 58%
rename from index.js
rename to index.ts
index c1485a9..96da09f 100644
--- a/index.js
+++ b/index.ts
@@ -3,40 +3,253 @@ import {
   Platform,
   NativeEventEmitter,
   DeviceEventEmitter,
+  EmitterSubscription,
 } from 'react-native';
 
-const ChannelModule = NativeModules.RNChannelIO;
+export type ChannelButtonIconType = 
+  | 'channel'
+  | 'chatBubbleFilled'
+  | 'chatProgressFilled'
+  | 'chatQuestionFilled'
+  | 'chatLightningFilled' 
+  | 'chatBubbleAltFilled'
+  | 'smsFilled'
+  | 'commentFilled'
+  | 'sendForwardFilled'
+  | 'helpFilled'
+  | 'chatProgress'
+  | 'chatQuestion'
+  | 'chatBubbleAlt'
+  | 'sms'
+  | 'comment'
+  | 'sendForward'
+  | 'communication'
+  | 'headset'
+
+export interface ChannelButtonOption {
+  xMargin?: number;
+  yMargin?: number;
+  position?: 'left' | 'right';
+  icon?: ChannelButtonIconType;
+}
+
+export interface BubbleOption {
+  position?: 'top' | 'bottom';
+  yMargin?: number;
+}
+
+export interface Profile extends Record<string, any> {}
+
+export type Language = 'ko' | 'ja' | 'en';
+
+export type Appearance = 'system' | 'light' | 'dark';
+
+export interface User {
+  id: string
+  memberId?: string
+  name?: string
+  avatarUrl?: string
+  profile?: Profile
+  alert: number
+  unread: number
+  tags?: string[]
+  language: Language
+  unsubscribeEmail?: boolean
+  unsubscribeTexting?: boolean
+}
+
+export interface PopupData {
+  chatId: string
+  avatarUrl: string
+  name: string
+  message: string
+}
+
+export interface UserData {
+  language: Language
+  tags?: string[]
+  profile?: Profile
+  profileOnce?: Record<string, any>
+  unsubscribeEmail: boolean
+  unsubscribeTexting: boolean
+}
+
+export interface BootConfig {
+  pluginKey: string;
+  memberId?: string;
+  memberHash?: string;
+  profile?: Profile;
+  language?: Language;
+  unsubscribeEmail?: boolean;
+  unsubscribeTexting?: boolean;
+  trackDefaultEvent?: boolean;
+  hidePopup?: boolean;
+  channelButtonOption?: ChannelButtonOption;
+  bubbleOption?: BubbleOption;
+  appearance?: Appearance;
+}
+
+interface BootSuccess {
+  status: 'SUCCESS';
+  user: User;
+}
+
+interface BootError {
+  status:
+      | 'NOT_INITIALIZED'
+      | 'NETWORK_TIMEOUT'
+      | 'NOT_AVAILABLE_VERSION'
+      | 'SERVICE_UNDER_CONSTRUCTION'
+      | 'REQUIRE_PAYMENT'
+      | 'ACCESS_DENIED'
+      | 'UNKNOWN_ERROR';
+  user: undefined;
+}
+
+type BootResult = BootSuccess | BootError
+
+interface UpdateUserResult {
+  error: string;
+  user: User;
+}
+
+interface TagsResult {
+  error: string;
+  user: User;
+}
+
+interface AddTagsResult extends TagsResult {}
+
+interface RemoveTagsResult extends TagsResult {}
+
+interface ChannelModuleType {
+  Event: {
+    ON_PRE_URL_CLICKED: string;
+    ON_URL_CLICKED: string;
+    ON_BADGE_CHANGED: string;
+    ON_POPUP_DATA_RECEIVED: string;
+    ON_FOLLOW_UP_CHANGED: string;
+    ON_PUSH_NOTIFICATION_CLICKED: string;
+    ON_SHOW_MESSENGER: string;
+    ON_HIDE_MESSENGER: string;
+    ON_CHAT_CREATED: string;
+  };
+  boot: (bootConfig: BootConfig) => Promise<BootResult>;
+  sleep: () => void;
+  shutdown: () => void;
+  showChannelButton: () => void;
+  hideChannelButton: () => void;
+  showMessenger: () => void;
+  hideMessenger: () => void;
+  openChat: (chatId?: string | null, payload?: string | null) => void;
+  openWorkflow: (workflowId?: string) => void;
+  track: (eventName: string, properties?: Record<string, any>) => void;
+  updateUser: (userData: UserData) => Promise<UpdateUserResult>;
+  addTags: (tags: string[]) => Promise<AddTagsResult>;
+  removeTags: (tags: string[]) => Promise<RemoveTagsResult>;
+  isBooted: () => Promise<boolean>;
+  setDebugMode: (enable: boolean) => void;
+  initPushToken: (token: string) => void;
+  isChannelPushNotification: (userInfo: Record<string, any>) => Promise<boolean>;
+  receivePushNotification: (userInfo: Record<string, any>) => Promise<void>;
+  hasStoredPushNotification: () => Promise<boolean>;
+  openStoredPushNotification: () => void;
+  setPage: (page?: string | null, profile?: Profile) => void;
+  resetPage: () => void;
+  setAppearance: (appearance: Appearance) => void;
+  hidePopup: () => void;
+  handleUrlClicked: (url: string) => void;
+  notifyPushNotificationClickSubscriberExistence: (exists: boolean) => void;
+  performDefaultPushNotificationClickAction: (userId: string, chatId: string) => void;
+}
+
+interface RNChannelIO extends Pick<ChannelModuleType, 
+  | 'boot'
+  | 'sleep'
+  | 'shutdown'
+  | 'showChannelButton'
+  | 'hideChannelButton'
+  | 'showMessenger'
+  | 'hideMessenger'
+  | 'openChat'
+  | 'openWorkflow'
+  | 'track'
+  | 'updateUser'
+  | 'addTags'
+  | 'removeTags'
+  | 'isBooted'
+  | 'setDebugMode'
+  | 'initPushToken'
+  | 'isChannelPushNotification'
+  | 'receivePushNotification'
+  | 'hasStoredPushNotification'
+  | 'openStoredPushNotification'
+  | 'setPage'
+  | 'resetPage'
+  | 'setAppearance'
+  | 'hidePopup'> {
+  show: (animated: boolean) => void;
+  hide: (animated: boolean) => void;
+  open: (animated: boolean) => void;
+  close: (animated: boolean) => void;
+  handlePushNotification: (userInfo: Record<string, any>) => Promise<void>;
+  onChangeBadge: (cb?: (unread: number, alert: number) => void) => void;
+  onBadgeChanged: (cb?: (unread: number, alert: number) => void) => void;
+  onReceivePush: (cb?: (popup: PopupData) => void) => void;
+  onPopupDataReceived: (cb?: (popup: PopupData) => void) => void;
+  onClickChatLink: (handle: boolean, cb?: (url: string) => void) => void;
+  onUrlClicked: (cb?: (url: string, next: () => void) => void) => void;
+  onChangeProfile: (cb?: () => void) => void;
+  onProfileChanged: (cb?: (data: Record<string, any>) => void) => void;
+  onFollowUpChanged: (cb?: (data: Record<string, any>) => void) => void;
+  onPushNotificationClicked: (cb?: (chatId: string, next: () => void) => void) => void;
+  willShowMessenger: (cb?: () => void) => void;
+  onShowMessenger: (cb?: () => void) => void;
+  willHideMessenger: (cb?: () => void) => void;
+  onHideMessenger: (cb?: () => void) => void;
+  onChatCreated: (cb?: (chatId: string) => void) => void;
+}
+
+type Subscriber = EmitterSubscription | null | ((data: { url: string }) => void)
+
+const ChannelModule = NativeModules.RNChannelIO as ChannelModuleType;
 const ChannelEventEmitter = Platform.select({
   ios: new NativeEventEmitter(NativeModules.RNChannelIO),
   android: DeviceEventEmitter,
 });
 
-var subscribers = {};
+const subscribers: {
+  [key: string]: Subscriber;
+} = {}
 
-const replaceSubscriber = (type, newSubscriber) => {
+const replaceSubscriber = (type: string, newSubscriber?: Subscriber) => {
   const oldSubscriber = subscribers[type];
-  if (oldSubscriber && typeof oldSubscriber.remove === 'function') {
+  if (oldSubscriber && 'remove' in oldSubscriber && typeof oldSubscriber.remove === 'function') {
     oldSubscriber.remove();
   }
-  subscribers[type] = newSubscriber;
+  if (newSubscriber) {
+    subscribers[type] = newSubscriber;
+  } else {
+    delete subscribers[type];
+  }
 }
 
-const hasSubscriber = (type) => {
+const hasSubscriber = (type: string) => {
   return !!subscribers[type]
 }
 
-ChannelEventEmitter.addListener(ChannelModule.Event.ON_PRE_URL_CLICKED, (data) => {
+ChannelEventEmitter?.addListener(ChannelModule.Event.ON_PRE_URL_CLICKED, (data: { url: string }) => {
   if (!hasSubscriber(ChannelModule.Event.ON_URL_CLICKED)) {
     ChannelModule.handleUrlClicked(data.url);
   } else {
     const subscriber = subscribers[ChannelModule.Event.ON_URL_CLICKED];
     if (typeof subscriber === 'function') {
-      subscriber(data);
+      (subscriber as (data: { url: string }) => void)(data);
     }
   }
 });
 
-export const ChannelIO = {
+export const ChannelIO: RNChannelIO = {
 
   /**
    * Boot `ChannelIO`
@@ -44,7 +257,7 @@ export const ChannelIO = {
    * @param bootConfig BootConfig object contains information for booting
    * @returns A promise that returns status and guest info
    */
-  boot: async (bootConfig) => {
+  boot: async (bootConfig: BootConfig) => {
     return ChannelModule.boot(bootConfig);
   },
 
@@ -67,7 +280,7 @@ export const ChannelIO = {
    * Show `ChannelIO` button
    * @param {Boolean} aniamted Animate the launcher if true
    */
-  show: (animated) => {
+  show: (animated: boolean) => {
     console.log('ChannelIO', 'ChannelIO.show(animated) is deprecated. Please use ChannelIO.showChannelButton()')
     ChannelModule.showChannelButton()
   },
@@ -81,7 +294,7 @@ export const ChannelIO = {
    * Hide `ChannelIO` button
    * @param {Boolean} aniamted Animate the launcher if true
    */
-  hide: (animated) => {
+  hide: (animated: boolean) => {
     console.log('ChannelIO', 'ChannelIO.hide(animated) is deprecated. Please use ChannelIO.hideChannelButton()')
     ChannelModule.hideChannelButton()
   },
@@ -95,7 +308,7 @@ export const ChannelIO = {
    * Open `ChannelIO` messenger
    * @param {Boolean} aniamted Animate messenger if true
    */
-  open: (animated) => {
+  open: (animated: boolean) => {
     console.log('ChannelIO', 'ChannelIO.open(animated) is deprecated. Please use ChannelIO.showMessenger()')
     ChannelModule.showMessenger()
   },
@@ -109,7 +322,7 @@ export const ChannelIO = {
    * Close `ChannelIO` messenger
    * @param {Boolean} Animate messenger if true
    */
-  close: (animated) => {
+  close: (animated: boolean) => {
     console.log('ChannelIO', 'ChannelIO.close(animated) is deprecated. Please use ChannelIO.hideMessenger()')
     ChannelModule.hideMessenger()
   },
@@ -123,7 +336,7 @@ export const ChannelIO = {
    * @param {String} chatId user chat id
    * @param {String} payload auto fill message
    */
-  openChat: (chatId, payload) => {
+  openChat: (chatId?: string | null, payload?: string | null) => {
     if (typeof payload === 'string') {
       ChannelModule.openChat(chatId, payload);
     } else {
@@ -140,7 +353,7 @@ export const ChannelIO = {
    * - If you don't pass workflowId, no action is taken.
    * @param {String} workflowId The ID of workflow to start with. An error page will be shown if such workflow does not exist.
    */
-  openWorkflow: (workflowId) => {
+  openWorkflow: (workflowId?: string) => {
     ChannelModule.openWorkflow(workflowId);
   },
 
@@ -149,14 +362,14 @@ export const ChannelIO = {
    * @param {String} eventName event name
    * @param {Object} properties a json object contains information
    */
-  track: (eventName, properties) => ChannelModule.track(eventName, properties),
+  track: (eventName: string, properties?: Record<string, any>) => ChannelModule.track(eventName, properties),
 
   /**
    * Update user
    * @param userData userData object contains user data information for updating
    * @returns A promise that returns exception or user info
    */
-  updateUser: async (userData) => {
+  updateUser: async (userData: UserData) => {
     return ChannelModule.updateUser(userData)
   },
 
@@ -165,7 +378,7 @@ export const ChannelIO = {
    * @param tags tags object contains tags information for adding
    * @returns A promise that returns exception or user data
    */
-  addTags: async (tags) => {
+  addTags: async (tags: string[]) => {
     return ChannelModule.addTags(tags)
   },
 
@@ -174,7 +387,7 @@ export const ChannelIO = {
    * @param tags tags object contains tags information for removing
    * @returns A promise that returns exception or user data
    */
-  removeTags: async (tags) => {
+  removeTags: async (tags: string[]) => {
     return ChannelModule.removeTags(tags)
   },
 
@@ -190,27 +403,27 @@ export const ChannelIO = {
    * Set debug mode for native module
    * @param {Boolean} enable True if you want to set debug mode, otherwise false
    */  
-  setDebugMode: (enable) => ChannelModule.setDebugMode(enable),
+  setDebugMode: (enable: boolean) => ChannelModule.setDebugMode(enable),
 
   /**
    * Initialize push token
    * @param {String} token a push token
    */
-  initPushToken: (token) => ChannelModule.initPushToken(token),
+  initPushToken: (token: string) => ChannelModule.initPushToken(token),
 
   /**
    * Check whether a push data is for channel
    * @param {Object} userInfo userInfo part from push data
    * @returns {Boolean} true if the userInfo indicates `ChannelIO'`s push, otherwise false
    */
-  isChannelPushNotification: async (userInfo) => ChannelModule.isChannelPushNotification(userInfo),
+  isChannelPushNotification: async (userInfo: Record<string, any>) => ChannelModule.isChannelPushNotification(userInfo),
   
   /**
    * @deprecated
    * Handle `ChannelIO` push notification
    * @param {Object} userInfo userInfo part from push data
    */
-  handlePushNotification: async (userInfo) => {
+  handlePushNotification: async (userInfo: Record<string, any>) => {
     console.log('ChannelIO', 'ChannelIO.handlePushNotification(userInfo) is deprecated. Please use ChannelIO.receivePushNotification(userInfo)')
     ChannelModule.receivePushNotification(userInfo)
   },
@@ -218,7 +431,7 @@ export const ChannelIO = {
    * Receive `ChannelIO` push notification
    * @param {Object} userInfo userInfo part from push data
    */
-  receivePushNotification: async (userInfo) => ChannelModule.receivePushNotification(userInfo),
+  receivePushNotification: async (userInfo: Record<string, any>) => ChannelModule.receivePushNotification(userInfo),
 
   /**
    * Check whether a push data has stored
@@ -238,7 +451,7 @@ export const ChannelIO = {
    *     - When nil is assigned to a specific field within the profile object, only the value of that field is cleared.
    *     - The user chat profile value is applied when a user chat is created.
    */
-  setPage: (page, profile) => {
+  setPage: (page?: string | null, profile?: Profile) => {
     if (typeof page === "string") {
       ChannelModule.setPage(page, profile)
     } else if (page === null || page === undefined) {
@@ -257,7 +470,7 @@ export const ChannelIO = {
    * Sets the appearance of the SDK.
    * @param {String} appearance system | light | dark
    */
-  setAppearance: (appearance) => {
+  setAppearance: (appearance: Appearance) => {
     if (typeof appearance === "string") {
       ChannelModule.setAppearance(appearance)
     } else {
@@ -275,10 +488,10 @@ export const ChannelIO = {
    * Event listener that triggers when badge count has been changed
    * @param {Function} cb a callback function that takes a integer badge count as parameter
    */
-  onChangeBadge: (cb) => {
+  onChangeBadge: (cb?: (unread: number, alert: number) => void) => {
     console.log('ChannelIO', 'ChannelIO.onChangeBadge(cb) is deprecated. Please use ChannelIO.onBadgeChanged(cb)')
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_BADGE_CHANGED, (data) => {
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_BADGE_CHANGED, (data) => {
         cb(data.unread, data.alert);
       });
       replaceSubscriber(ChannelModule.Event.ON_BADGE_CHANGED, subscription);
@@ -291,9 +504,9 @@ export const ChannelIO = {
    * Event listener that triggers when badge count has been changed
    * @param {Function} cb a callback function that takes a integer badge count as parameter
    */
-  onBadgeChanged: (cb) => {
+  onBadgeChanged: (cb?: (unread: number, alert: number) => void) => {
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_BADGE_CHANGED, (data) => {
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_BADGE_CHANGED, (data) => {
         cb(data.unread, data.alert);
       });
       replaceSubscriber(ChannelModule.Event.ON_BADGE_CHANGED, subscription);
@@ -307,10 +520,10 @@ export const ChannelIO = {
    * Event listener that triggers when in-app popup has been arrived
    * @param {Function} cb a callback function that takes a object popup data as parameter
    */
-  onReceivePush: (cb) => {
+  onReceivePush: (cb?: (popup: PopupData) => void) => {
     console.log('ChannelIO', 'ChannelIO.onReceivePush(cb) is deprecated. Please use ChannelIO.onPopupDataReceived(cb)')
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_POPUP_DATA_RECEIVED, (data) => {
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_POPUP_DATA_RECEIVED, (data) => {
         cb(data.popup);
       });
       replaceSubscriber(ChannelModule.Event.ON_POPUP_DATA_RECEIVED, subscription);
@@ -322,9 +535,9 @@ export const ChannelIO = {
    * Event listener that triggers when in-app popup has been arrived
    * @param {Function} cb a callback function that takes a object popup data as parameter
    */
-  onPopupDataReceived: (cb) => {
+  onPopupDataReceived: (cb?: (popup: PopupData) => void) => {
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_POPUP_DATA_RECEIVED, (data) => {
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_POPUP_DATA_RECEIVED, (data) => {
         cb(data.popup);
       });
       replaceSubscriber(ChannelModule.Event.ON_POPUP_DATA_RECEIVED, subscription);
@@ -339,7 +552,7 @@ export const ChannelIO = {
    * @param {Boolean} handle True if you want to handle a link, otherwise false
    * @param {Function} cb a callback function that takes a string url as parameter
    */
-  onClickChatLink: (handle, cb) => {
+  onClickChatLink: (handle: boolean, cb?: (url: string) => void) => {
     console.log('ChannelIO', 'ChannelIO.onClickChatLink(handle, cb) is deprecated. Please use ChannelIO.onUrlClicked(cb)')
     if (cb) {
       replaceSubscriber(ChannelModule.Event.ON_URL_CLICKED, (data) => {
@@ -356,7 +569,7 @@ export const ChannelIO = {
    * Event listener that triggers when a url has been clicked by a user
    * @param {Function} cb a callback function that takes a string url as parameter
    */
-  onUrlClicked: (cb) => {
+  onUrlClicked: (cb?: (url: string, next: () => void) => void) => {
     if (cb) {
       replaceSubscriber(ChannelModule.Event.ON_URL_CLICKED, (data) => {
         const next = () => {
@@ -373,7 +586,7 @@ export const ChannelIO = {
    * @deprecated
    * 'onChangeProfile' is deprecated. Please use 'onFollowUpChanged'.
    */
-  onChangeProfile: (cb) => {
+  onChangeProfile: (cb?: () => void) => {
     console.warn("'onChangeProfile' is deprecated. Please use 'onFollowUpChanged'.")
   },  
 
@@ -381,7 +594,7 @@ export const ChannelIO = {
    * @deprecated
    * 'onProfileChanged' is deprecated. Please use 'onFollowUpChanged'.
    */
-  onProfileChanged: (cb) => {
+  onProfileChanged: (cb?: (data: Record<string, any>) => void) => {
     console.warn("'onProfileChanged' is deprecated. Please use 'onFollowUpChanged'.")
   },
 
@@ -389,9 +602,9 @@ export const ChannelIO = {
    * Event listener that triggers when guest profile is updated
    * @param {Function} cb a callback function that takes a map
    */
-  onFollowUpChanged: (cb) => {
+  onFollowUpChanged: (cb?: (data: Record<string, any>) => void) => {
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_FOLLOW_UP_CHANGED, (data) => {
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_FOLLOW_UP_CHANGED, (data) => {
         cb(data);
       });
       replaceSubscriber(ChannelModule.Event.ON_FOLLOW_UP_CHANGED, subscription);
@@ -407,11 +620,11 @@ export const ChannelIO = {
    *
    * @param {Function} cb a callback function
    */
-  onPushNotificationClicked: (cb) => {
+  onPushNotificationClicked: (cb?: (chatId: string, next: () => void) => void) => {
     if (Platform.OS !== 'android') { return }
 
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_PUSH_NOTIFICATION_CLICKED, data => {
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_PUSH_NOTIFICATION_CLICKED, data => {
         const next = () => ChannelModule.performDefaultPushNotificationClickAction(data.userId, data.chatId);
 
         cb(data.chatId, next);
@@ -430,10 +643,10 @@ export const ChannelIO = {
    * Event listener that triggers when `ChannelIO` messenger is about to display
    * @param {Function} cb a callback function
    */
-  willShowMessenger: (cb) => {
+  willShowMessenger: (cb?: () => void) => {
     console.log('ChannelIO', 'ChannelIO.willShowMessenger(cb) is deprecated. Please use ChannelIO.onShowMessenger(cb)')
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_SHOW_MESSENGER, cb);
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_SHOW_MESSENGER, cb);
       replaceSubscriber(ChannelModule.Event.ON_SHOW_MESSENGER, subscription);
     } else {
       replaceSubscriber(ChannelModule.Event.ON_SHOW_MESSENGER, null);
@@ -443,9 +656,9 @@ export const ChannelIO = {
    * Event listener that triggers when `ChannelIO` messenger is about to display
    * @param {Function} cb a callback function
    */
-  onShowMessenger: (cb) => {
+  onShowMessenger: (cb?: () => void) => {
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_SHOW_MESSENGER, cb);
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_SHOW_MESSENGER, cb);
       replaceSubscriber(ChannelModule.Event.ON_SHOW_MESSENGER, subscription);
     } else {
       replaceSubscriber(ChannelModule.Event.ON_SHOW_MESSENGER, null);
@@ -457,10 +670,10 @@ export const ChannelIO = {
    * Event listener that triggers when `ChannelIO` messenger is about to dismiss
    * @param {Function} cb a callback function
    */
-  willHideMessenger: (cb) => {
+  willHideMessenger: (cb?: () => void) => {
     console.log('ChannelIO', 'ChannelIO.willHideMessenger(cb) is deprecated. Please use ChannelIO.onHideMessenger(cb)')
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_HIDE_MESSENGER, cb);
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_HIDE_MESSENGER, cb);
       replaceSubscriber(ChannelModule.Event.ON_HIDE_MESSENGER, subscription);
     } else {
       replaceSubscriber(ChannelModule.Event.ON_HIDE_MESSENGER, null);
@@ -470,9 +683,9 @@ export const ChannelIO = {
    * Event listener that triggers when `ChannelIO` messenger is about to dismiss
    * @param {Function} cb a callback function
    */
-  onHideMessenger: (cb) => {
+  onHideMessenger: (cb?: () => void) => {
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_HIDE_MESSENGER, cb);
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_HIDE_MESSENGER, cb);
       replaceSubscriber(ChannelModule.Event.ON_HIDE_MESSENGER, subscription);
     } else {
       replaceSubscriber(ChannelModule.Event.ON_HIDE_MESSENGER, null);
@@ -483,9 +696,9 @@ export const ChannelIO = {
    * Event listener that triggers when a chat has been created by a user
    * @param {Function} cb a callback function that takes a string chat id as parameter
    */
-  onChatCreated: (cb) => {
+  onChatCreated: (cb?: (chatId: string) => void) => {
     if (cb) {
-      const subscription = ChannelEventEmitter.addListener(ChannelModule.Event.ON_CHAT_CREATED, (data) => {
+      const subscription = ChannelEventEmitter?.addListener(ChannelModule.Event.ON_CHAT_CREATED, (data) => {
         cb(data.chatId);
       });
       replaceSubscriber(ChannelModule.Event.ON_CHAT_CREATED, subscription);