React + Socket IO: Accessing the first message

I'm trying to create an auto reply after a user has sent his first message. I have no problems with the reply, it's just knowing when the a user has sent his first message (and first message only).

I have an USER prop that contains users id.

here is my hook that is responsible for the message sending

  useEffect(() => {
    if (socket) {
      socket.on("msg", msg=> {
        dispatch({
          type: ACTIONS.MSG,
          value: msg
        });
      });

in the reducer the messages is an array. So I've been thinking of just creating something like

   PSEUDO CODE if (the user PROP.Type === 'userType1' && sends.message[0]) {
    return autoReply
    }