Receiving messages with CometChat has two parts:
  1. Adding a listener to receive real-time messages when your app is running
  2. Calling a method to retrieve missed messages when your app was not running

​
Real-Time Messages

In other words, as a recipient, how do I receive messages when my app is running? To receive real-time incoming messages, you need to register the MessageListener wherever you wish to receive the incoming messages. You can use the addMessageListener() method to do so. 
let listenerID = "UNIQUE_LISTENER_ID";

CometChat.addMessageListener(
  listenerID,
  new CometChat.MessageListener({
    onTextMessageReceived: (textMessage) => {
      console.log("Text message received successfully", textMessage);
    },
    onMediaMessageReceived: (mediaMessage) => {
      console.log("Media message received successfully", mediaMessage);
    },
    onCustomMessageReceived: (customMessage) => {
      console.log("Custom message received successfully", customMessage);
    },
  })
);
ParameterDescription
listenerIdAn ID that uniquely identifies that listener.
We recommend you remove the listener once you don’t want to receive a message for particular listener. You can remove the listener in componentWillUnmount() method. 
var listenerID = "UNIQUE_LISTENER_ID";

CometChat.removeMessageListener(listenerID);
As a sender, you will not receive your own message in a real-time message event. However, if a user is logged-in using multiple devices, they will receive an event for their own message in other devices.

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Missed Messages

In other words, as a recipient, how do I receive messages that I missed when my app was not running? For most use cases, you will need to add functionality to load missed messages. If you’re building an on-demand or live streaming app, you may choose to skip this and fetch message history instead. Using the same MessagesRequest class and the filters provided by the MessagesRequestBuilder class, you can fetch the message that we sent to the logged-in user but were not delivered to him as he was offline. For this, you will require the Id of the last message received. You can either maintain it at your end or use the getLastDeliveredMessageId() method provided by the CometChat class. This Id needs to be passed to the setMessageId() method of the builder class. Now using the fetchNext() method, you can fetch all the messages that were sent to the user when he/she was offline. Calling the fetchNext() method on the same object repeatedly allows you to fetch all the offline messages for the logged in user.

​
For a Particular One-on-one Conversation

let UID = "UID";
let limit = 30;
let latestId = await CometChat.getLastDeliveredMessageId();

var messagesRequest = new CometChat.MessagesRequestBuilder()
  .setUID(UID)
  .setMessageId(latestId)
  .setLimit(limit)
  .build();

messagesRequest.fetchNext().then(
  (messages) => {
    console.log("Message list fetched:", messages);
  },
  (error) => {
    console.log("Message fetching failed with error:", error);
  }
);

​
For a Particular Group

let GUID = "GUID";
let limit = 30;
let latestId = await CometChat.getLastDeliveredMessageId();

var messagesRequest = new CometChat.MessagesRequestBuilder()
  .setGUID(GUID)
  .setMessageId(latestId)
  .setLimit(limit)
  .build();

messagesRequest.fetchNext().then(
  (messages) => {
    console.log("Message list fetched:", messages);
  },
  (error) => {
    console.log("Message fetching failed with error:", error);
  }
);

​
Unread Messages

In other words, as a logged-in user, how do I fetch the messages I’ve not read? Using the MessagesRequest class described above, you can fetch the unread messages for the logged in user. In order to achieve this, you need to set the unread variable in the builder to true using the setUnread() method so that only the unread messages are fetched.

​
For a Particular One-on-one Conversation

let UID = "UID";
let limit = 30;
let messagesRequest = new CometChat.MessagesRequestBuilder()
  .setUID(UID)
  .setUnread(true)
  .setLimit(limit)
  .build();

messagesRequest.fetchPrevious().then(
  (messages) => {
    console.log("Message list fetched:", messages);
  },
  (error) => {
    console.log("Message fetching failed with error:", error);
  }
);

​
For a Particular Group

let GUID = "GUID";
let limit = 30;
let messagesRequest = new CometChat.MessagesRequestBuilder()
  .setGUID(GUID)
  .setUnread(true)
  .setLimit(limit)
  .build();

messagesRequest.fetchPrevious().then(
  (messages) => {
    console.log("Message list fetched:", messages);
  },
  (error) => {
    console.log("Message fetching failed with error:", error);
  }
);
Base MessageThe list of messages received is in the form of objects of BaseMessage class. A BaseMessage can either be an object of the TextMessage, MediaMessage, CustomMessage, Action or Call class. You can use the instanceOf operator to check the type of object.

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Message History

In other words, as a logged-in user, how do I fetch the complete message history?

​
For a Particular One-on-one Conversation

Using the MessagesRequest class and the filters for the MessagesRequestBuilder class as shown in the below code snippet, you can fetch the entire conversation between the logged in user and any particular user. For this use case, it is mandatory to set the UID parameter using the setUID() method of the builder. This UID is the unique id of the user for which the conversation needs to be fetched. 
let UID = "UID";
let limit = 30;
let messagesRequest = new CometChat.MessagesRequestBuilder()
  .setUID(UID)
  .setLimit(limit)
  .build();

messagesRequest.fetchPrevious().then(
  (messages) => {
    console.log("Message list fetched:", messages);
  },
  (error) => {
    console.log("Message fetching failed with error:", error);
  }
);
Calling the fetchPrevious() method on the same object repeatedly allows you to fetch the entire conversation between the logged in user and the specified user. This can be implemented with upward scrolling to display the entire conversation.

​
For a Particular Group

Using the MessagesRequest class and the filters for the MessagesRequestBuilder class as shown in the below code snippet, you can fetch the entire conversation for any group provided you have joined the group. For this use case, it is mandatory to set the GUID parameter using the setGUID() method of the builder. This GUID is the unique identifier of the Group for which the messages are to be fetched. 
let GUID = "GUID";
let limit = 30;
let messagesRequest = new CometChat.MessagesRequestBuilder()
  .setGUID(GUID)
  .setLimit(limit)
  .build();

messagesRequest.fetchPrevious().then(
  (messages) => {
    console.log("Message list fetched:", messages);
  },
  (error) => {
    console.log("Message fetching failed with error:", error);
  }
);
Calling the fetchPrevious() method on the same object repeatedly allows you to fetch the entire conversation for the group. This can be implemented with upward scrolling to display the entire conversation.

​
Search Messages

In other words, as a logged-in user, how do I search a message? In order to do this, you can use the setSearchKeyword() method. This method accepts string as input. When set, the SDK will fetch messages which match the searchKeyword.
By default, the searchKey is searched only in message text. However, if you enable Conversation & Advanced Search, the searchKey will be searched in message text, file name, mentions & mime type of the file.The Conversation & Advanced Search is only available in Advanced & Custom plans. If you’re already on one of these plans, please enable the Conversation & Advanced Search from CometChat Dashboard (Open your app, navigate to Chats -> Settings -> General Configuration)
FeatureBasic SearchAdvance Search
Text search✅✅
File name search❌✅
Mentions search❌✅
Mime type search❌✅

​
For a Particular One-on-one Conversation

let UID = "UID";
let limit = 30;
let searchKeyword = "Hello";
let messagesRequest = new CometChat.MessagesRequestBuilder()
  .setUID(UID)
  .setLimit(limit)
  .setSearchKeyword(searchKeyword)
  .build();

messagesRequest.fetchPrevious().then(
  (messages) => {
    console.log("Message list fetched:", messages);
  },
  (error) => {
    console.log("Message fetching failed with error:", error);
  }
);

​
For a Particular Group

let GUID = "GUID";
let limit = 30;
let searchKeyword = "Hello";
let messagesRequest = new CometChat.MessagesRequestBuilder()
  .setGUID(GUID)
  .setLimit(limit)
  .setSearchKeyword(searchKeyword)
  .build();

messagesRequest.fetchPrevious().then(
  (messages) => {
    console.log("Message list fetched:", messages);
  },
  (error) => {
    console.log("Message fetching failed with error:", error);
  }
);

​
Unread Message Count

In other words, as a logged-in user, how do I find out the number of unread messages that I have?

​
For a Particular One-on-one Conversation

In other words, how do I find out the number of unread messages I have from a particular user? In order to get the unread message count for a particular user, you can use the getUnreadMessageCountForUser(). This method has the below two variants: 
CometChat.getUnreadMessageCountForUser(UID);
If you wish to ignore the messages from blocked users you can use the below syntax setting the boolean parameter to true: 
CometChat.getUnreadMessageCountForUser(UID, hideMessagesFromBlockedUsers);

let UID = "UID";

CometChat.getUnreadMessageCountForUser(UID).then(
  (unreadMessageCountObject) => {
    console.log("Unread message count fetched", unreadMessageCountObject);
  },
  (error) => {
    console.log("Error in getting unread message count", error);
  }
);
It will return an object which will contain the UID as the key and the unread message count as the value.

​
For a Particular Group Conversation

In other words, how do I find out the number of unread messages I have in a single group? In order to get the unread message count for a particular group, you can use the getUnreadMessageCountForGroup(). This method has the below two variants: 
CometChat.getUnreadMessageCountForGroup(GUID);
“ If you wish to ignore the messages from blocked users you can use the below syntax setting the boolean parameter to true: 
CometChat.getUnreadMessageCountForGroup(GUID, hideMessagesFromBlockedUsers);

let GUID = "GUID";

CometChat.getUnreadMessageCountForGroup(GUID).then(
  (unreadMessageCountObject) => {
    console.log("Unread message count fetched", unreadMessageCountObject);
  },
  (error) => {
    console.log("Error in getting unread message count", error);
  }
);
It will return an object which will contain the GUID as the key and the unread message count as the value.

​
For All One-on-one & Group Conversations

In other words, how do I find out the number of unread messages for every one-on-one and group conversation? In order to get all the unread message count combined i.e unread message counts for all the users and groups, you can use the getUnreadMessageCount() method. This method has two variants: 
CometChat.getUnreadMessageCount();
If you wish to ignore the messages from blocked users you can use the below syntax setting the boolean parameter to true: 
CometChat.getUnreadMessageCount(hideMessagesFromBlockedUsers);

CometChat.getUnreadMessageCount().then(
  (unreadMessageCountObject) => {
    console.log("Unread message count fetched", unreadMessageCountObject);
  },
  (error) => {
    console.log("Error in getting unread message count", error);
  }
);
It returns an object having two keys:
  1. users - The value for this key holds another object that holds the UID as key and their corresponding unread message count as value.
  2. groups - The value for this key holds another object that holds the GUID as key and their corresponding unread message count as value.

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For All One-on-one Conversations

In order to fetch the unread message counts for just the users, you can use the getUnreadMessageCountForAllUsers() method. This method just like others has two variants: 
CometChat.getUnreadMessageCountForAllUsers();
If you wish to ignore the messages from blocked users you can use the below syntax setting the boolean parameter to true: 
CometChat.getUnreadMessageCountForAllUsers(hideMessagesFromBlockedUsers);

CometChat.getUnreadMessageCountForAllUsers().then(
  (unreadMessageCountObject) => {
    console.log("Unread message count fetched", unreadMessageCountObject);
  },
  (error) => {
    console.log("Error in getting unread message count", error);
  }
);
It returns an object which will contain the UID as the key and the unread message count as the value.

​
For All Group Conversations

In order to fetch the unread message counts for just the groups, you can use the getUnreadMessageCountForAllGroups() method. This method just like others has two variants: 
CometChat.getUnreadMessageCountForAllGroups();
If you wish to ignore the messages from blocked users you can use the below syntax setting the boolean parameter to true: 
CometChat.getUnreadMessageCountForAllGroups(hideMessagesFromBlockedUsers);

CometChat.getUnreadMessageCountForAllGroups().then(
  (unreadMessageCountObject) => {
    console.log("Unread message count fetched", unreadMessageCountObject);
  },
  (error) => {
    console.log("Error in getting unread message count", error);
  }
);
It returns an object which will contain the GUID as the key and the unread message count as the value.