It looks like this is my backend for the chat messaging app any idea of this problem? I wanted to display the name of who chatted me 
 loadMessages(callback) {
    this.messagesRef = firebase.database().ref("messages");
    this.messagesRef.off();
    const onReceive = data => {
      const message = data.val();
      callback({
        id: data.key,
        text: message.text,
        createdAt: message.createdAt,
        user: {
          _id: message.user._id,
          name: message.user.Uemail,
        }
      });
    };