chat.on(eventName, handler, context);

let onMessageReceived = function(event) {
  // event.data - An array that stores `Message` objects - [Message]
  // For details of Message, please refer to https://www.tencentcloud.com/document/product/1047/47990
  const messageList = event.data;
  messageList.forEach((message) => {
    if (message.type === TencentCloudChat.TYPES.MSG_TEXT) {
      // Text message
    } else if (message.type === TencentCloudChat.TYPES.MSG_IMAGE) {
      // Image message
    } else if (message.type === TencentCloudChat.TYPES.MSG_AUDIO) {
      // Audio message
    } else if (message.type === TencentCloudChat.TYPES.MSG_VIDEO) {
      // Video message
    } else if (message.type === TencentCloudChat.TYPES.MSG_FILE) {
      // File message
    } else if (message.type === TencentCloudChat.TYPES.MSG_CUSTOM) {
      // Custom message
    } else if (message.type === TencentCloudChat.TYPES.MSG_MERGER) {
      // Merged message
    } else if (message.type === TencentCloudChat.TYPES.MSG_LOCATION) {
      // Geographical location message
    } else if (message.type === TencentCloudChat.TYPES.MSG_GRP_TIP) {
      // Group tip message
    } else if (message.type === TencentCloudChat.TYPES.MSG_GRP_SYS_NOTICE) {
      // Group system notification
    }
  });
};
chat.on(TencentCloudChat.EVENT.MESSAGE_RECEIVED, onMessageReceived);

chat.off(eventName, handler, context);

let onMessageReceived = function(event) {
  // event.name - TencentCloudChat.EVENT.MESSAGE_RECEIVED
  // event.data - An array that stores `Message` objects - [Message]
};
chat.off(TencentCloudChat.EVENT.MESSAGE_RECEIVED, onMessageReceived);