realtime-chat-server-2.js

// server.get('*') is here ...

const chatHistory = { messages: [] };

server.post('/message', (req, res, next) => {
  const { user = null, message = '', timestamp = +new Date } = req.body;
  const sentimentScore = sentiment(message).score;

  const chat = { user, message, timestamp, sentiment: sentimentScore };

  chatHistory.messages.push(chat);
  pusher.trigger('chat-room', 'new-message', { chat });
});

server.post('/messages', (req, res, next) => {
  res.json({ ...chatHistory, status: 'success' });
});

// server.listen() is here ...