// ---------- model (Book.js) --------
// ...
const bookSchema = new mongoose.Schema({
  title: {
      type: 'string',
      require: 'true'
  },
  author: {
      type: 'string',
      require: 'true'
  },
  price: {
      type: 'number',
      min: 1
  }
});

// ---------- controller -----
// ....
postCreate: function (req, res) {
    Book.create(req.body)
      .then(() => res.redirect('/'))
      .catch((err) => console.log(err));
  },

/* ------ Mongo server log ---
 ...
2019-04-11T10:21:17.725+0000 I NETWORK  [listener] connection accepted from 127.0.0.1:48586 #2 (1 connection now open)
2019-04-11T10:21:17.727+0000 I NETWORK  [conn2] received client metadata from 127.0.0.1:48586 conn2: { driver: { name: "nodejs", version: "3.2.2" }, os: { ... }, platform: "Node.js v6.11.2, LE, mongodb-core: 3.2.2" }
*/