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+# What's new in version 4?
+
+## Overall
+
+- No callback. Use `Promise`.
+
+```ts
+// v3
+sb.connect(userId, (err, user) => {});
+
+// v4
+const user = await sb.connect(userId);
+```
+
+- `Treeshaking` applied. The classes, interfaces, enums, types come to be `import`-able with treeshaking. See [SDK reference](https://sendbird.com/docs/chat/v4/javascript/ref/index.html) page for detailed list of exports.
+
+```ts
+// v3
+sb.GroupChannel
+sb.LogLevel
+...
+
+// v4
+import { LogLevel } from '@sendbird/chat';
+import { GroupChannel } from '@sendbird/groupChannel';
+...
+```
+
+- `static` object relocation.
+
+|`v3`|`v4`|
+|-|-|
+|`sb.GroupChannel`|`sb.groupChannel`*|
+|`sb.OpenChannel`|`sb.openChannel`**|
+|`sb.BaseMessage`|`sb.message`|
+
+> \* Should declare `GroupChannelModule` in `SendbirdChat.init()`.  
+> ** Should declare `OpenChannelModule` in `SendbirdChat.init()`.
+
+## New features
+
+- Added `onConnected()`, `onDisconnected()` to `ConnectionHandler`.
+
+## Changes
+
+- Changed initialization interface.
+
+```ts
+// v3
+import SendBird from 'sendbird';
+import AsyncStorage from '@react-native-async-storage/async-storage';
+
+const sb = new SendBird({
+  appId: APP_ID,
+  localCacheEnabled: true,
+});
+sb.setLogLevel(sb.LogLevel.WARN);
+sb.appVersion = APP_VERSION;
+sb.Options.useMemberAsMessageSender = true;
+
+// only for React Native
+sb.useAsyncStorageAsDatabase(AsyncStorage);
+
+// v4
+import SendbirdChat, {
+  SendbirdChatOptions,
+  Loglevel
+} from '@sendbird/chat';
+import AsyncStorage from '@react-native-async-storage/async-storage';
+
+const sb = SendbirdChat.init({
+  appId: APP_ID,
+  appVersion: APP_VERSION,
+  modules,
+  options: new SendbirdChatOptions({
+		useMemberAsMessageSender: true,
+	}),
+  logLevel: LogLevel.WARN,
+  localCacheEnabled: true,
+  useAsyncStorageStore: AsyncStorage, // only for React Native
+});
+```
+
+- Replaced `ChannelHandler` to `GroupChannelHandler` and `OpenChannelHandler`
+
+```ts
+// v3
+const channelHandler = new sb.ChannelHandler();
+channelHandler.onChannelChanged = (channel) => {
+	...
+};
+sb.addChannelHandler(EVENT_ID, channelHandler);
+sb.removeChannelHandler(EVENT_ID);
+
+// v4
+import { GroupChannelHandler } from '@sendbird/chat/groupChannel';
+
+const channelHandler = new GroupChannelHandler({
+	onChannelChanged: (channel) => {
+		...
+	},
+});
+sb.groupChannel.addGroupChannelHandler(EVENT_ID, channelHandler);
+sb.groupChannel.removeGroupChannelHandler(EVENT_ID);
+```
+
+- No builder pattern for `Collection`s.
+
+```ts
+// v3
+const groupChannelFilter = new sb.GroupChannelFilter();
+const gc = sb.GroupChannel.createGroupChannelCollection()
+  .setOrder(sb.GroupChannelCollection.GroupChannelOrder.LATEST_LAST_MESSAGE)
+  .setFilter(groupChannelFilter)
+  .build();
+
+const messageFilter = new sb.MessageFilter();
+const mc = channel.createMessageCollection()
+  .setFilter(messageFilter)
+  .setStartingPoint(startingPoint)
+  .build();
+
+// v4
+import {
+	GroupChannelFilter,
+	GroupChannelListOrder
+} from '@sendbird/chat/groupChannel';
+import { MessageFilter } from '@sendbird/chat/message';
+
+const groupChannelFilter = new GroupChannelFilter();
+const gc = sb.groupChannel.createGroupChannelCollection({
+	filter: groupChannelFilter,
+	order: GroupChannelListOrder.LATEST_LAST_MESSAGE,
+});
+
+const messageFilter = new MessageFilter();
+const mc = channel.createMessageCollection({
+	filter: messageFilter,
+	startingPoint: Date.now(),
+});
+```
+
+- Changed `sb.updateCurrentUserInfo()` to take `UserUpdateParams` as a parameter.
+
+```ts
+// v3
+sb.updateCurrentUserInfo(NICKNAME, PROFILE_URL);
+sb.updateCurrentUserInfoWithProfileImage(NICKNAME, PROFILE_IMAGE);
+
+// v4
+import { UserUpdateParams } from '@sendbird/chat';
+
+const params = new UserUpdateParams({
+	nickname: NICKNAME,
+	profileUrl: PROFILE_URL,
+	// or you can put a file as `profileImage` to upload the profile
+});
+sb.updateCurrentUserInfo(params);
+// no sb.updateCurrentUserInfoWithProfileImage()
+```
+
+- Changed `sb.getUnreadItemCount()` to take `UnreadItemCountParams` as a parameter.
+
+```ts
+// v3
+sb.getUnreadItemCount(KEYS);
+
+// v4
+const params = new UnreadItemCountParams({
+	keys: KEYS,
+});
+sb.getUnreadItemCount(params);
+```
+
+- Changed `sb.getTotalUnreadMessageCount()` to take `TotalUnreadMessageCountParams` as a parameter.
+
+```ts
+// v3
+sb.getTotalUnreadMessageCount(CHANNEL_CUSTOM_TYPES);
+// no super channel filter support
+
+// v4
+const params = new TotalUnreadMessageCountParams({
+	channelCustomTypesFilter: CHANNEL_CUSTOM_TYPES,
+	superChannelFilter: SUPER_CHANNEL_FILTER,
+});
+sb.getTotalUnreadMessageCount(params);
+```
+
+- Changed `sendUserMessage()` and `sendFileMessage()` interface to chain the callbacks for pending/failed/succeeded messages.
+
+```ts
+// v3
+const pendingMessage = channel.sendUserMessage(params, (err, message) => {
+	if (err) {
+		// message is a failed message
+	} else {
+		// message is a succeeded message
+	}
+});
+
+// v4
+channel.sendUserMessage(params)
+	.onPending((pendingMessage: UserMessage) => {})
+	.onFailed((err: Error, failedMessage: UserMessage) => {})
+	.onSucceeded((succeededMessage: UserMessage) => {});
+```
+
+- Separated update params from create params.
+
+```ts
+// v3
+GroupChannelParams // both for create/update
+OpenChannelParams // both for create/update
+UserMessageParams // both for send/update
+FileMessageParams // both for send/update
+
+// v4
+GroupChannelCreateParams
+GroupChannelUpdateParams
+OpenChannelCreateParams
+OpenChannelUpdateParams
+UserMessageCreateParams
+UserMessageUpdateParams
+FileMessageCreateParams
+FileMessageUpdateParams
+```
+
+- Changed to accept initial properties in `~Params` constructors.
+
+```ts
+// v3
+const params = new sb.UserMessageParams();
+params.message = 'message';
+
+// v4
+import { UserMessageParams } from '@sendbird/chat/message';
+
+const params = new UserMessageCreateParams({
+	message: 'message',
+});
+
+// or you can still use it as v3
+const params = new UserMessageCreateParams();
+params.message = 'message';
+```
+
+- Changed to accept properties in `~Query` constructors. The query properties are immutable later on.
+
+```ts
+// v3
+const query = sb.GroupChannel.createMyGroupChannelListQuery();
+query.customTypesFilter = ['a', 'b'];
+query.order = 'latest_last_message';
+
+// v4
+import { GroupChannelListOrder } from '@sendbird/chat/groupChannel';
+
+const query = sb.groupChannel.createMyGroupChannelListQuery({
+	customTypesFilter: ['a', 'b'],
+	order: GroupChannelListOrder.LATEST_LAST_MESSAGE,
+});
+query.customTypesFilter = ['a', 'b']; // ERROR! IMMUTABLE PROPERTY!
+```
+
+- Changed `buildFromSerializedData()` paths.
+
+```ts
+// v3
+sb.AdminMessage.buildFromSerializedData()
+sb.FileMessage.buildFromSerializedData()
+sb.UserMessage.buildFromSerializedData()
+sb.Sender.buildFromSerializedData()
+
+sb.GroupChannel.buildFromSerializedData()
+sb.GroupChannelListQuery.buildFromSerializedData()
+sb.Member.buildFromSerializedData()
+
+sb.OpenChannel.buildFromSerializedData()
+
+sb.User.buildFromSerializedData()
+
+// v4
+sb.message.buildMessageFromSerializedData() // admin/file/user altogether
+sb.message.buildSenderFromSerializedData()
+
+sb.groupChannel.buildGroupChannelFromSerializedData()
+sb.groupChannel.buildGroupChannelListQueryFromSerializedData()
+sb.groupChannel.buildMemberFromSerializedData()
+
+sb.openChannel.buildOpenChannelFromSerializedData()
+
+sb.buildUserFromSerializedData()
+```
+
+- Turned some getter functions to read-only properties.
+
+```ts
+// v3
+SendBird.getInstance()
+sb.getApplicationId()
+sb.getConnectionState()
+sb.getLastConnectedAt()
+channel.isGroupChannel()
+channel.isOpenChannel()
+channel.getCachedMetaData()
+message.isUserMessage()
+message.isFileMessage()
+message.isAdminMessage()
+message.isResendable()
+
+// v4
+SendbirdChat.instance
+sb.appId
+sb.connectionState
+sb.lastConnectedAt
+channel.isGroupChannel
+channel.isOpenChannel
+channel.cachedMetaData
+message.isUserMessage
+message.isFileMessage
+message.isAdminMessage
+message.isResendable
+```
+
+- Relocations
+
+|v3|v4|
+|-|-|
+|`sb.getMyGroupChannelChangeLogsByToken()`|`sb.groupChannel.getMyGroupChannelChangeLogsByToken()`|
+|`sb.getMyGroupChannelChangeLogsByTimestamp()`|`sb.groupChannel.getMyGroupChannelChangeLogsByTimestamp()`|
+
+- Renames
+
+|v3|v4|
+|-|-|
+|`SendBird`|`SendbirdChat`|
+|`SendBirdException`|`SendbirdError`|
+|`GCMPushToken`|`FCMPushToken`*|
+|`sb.initializeDatabase()`|`sb.initializeCache()`|
+|`sb.clearDatabase()`|`sb.clearCache()`|
+|`channelHandler.onReadReceiptUpdated()`|`groupChannelHandler.onUnreadMemberStatusUpdated()`|
+|`channelHandler.onDeliveryReceiptUpdated()`|`groupChannelHandler.onUndeliveredMemberStatusUpdated()`|
+|`groupChannel.cachedReadReceiptStatus`|`groupChannel.cachedUnreadMemberState`|
+|`groupChannel.cachedDeliveryReceiptStatus`|`groupChannel.cachedUndeliveredMemberState`|
+|`message.sendingStatus`|`message.requestState`|
+
+> \* But stilling meaning the token for Android.
+
+## Removes
+
+- Removed `channel.getMessagesByID()`.
\ No newline at end of file