const mongoose = require('mongoose')
mongoose.connect('mongodb://localhost:27017,localhost:27018,localhost:27019/test?replicaSet=rs0', { useNewUrlParser: true })
  .then(() => {
    var kittySchema = new mongoose.Schema({
      name: String
    });
    var Kitten = mongoose.model('Kitten', kittySchema);
    var silence = new Kitten({ name: 'Silence' });
    console.log(silence.name); // 'Silence'
    silence.save()
  })
  .catch(console.log)

var db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.on('connected', function() {
console.log('we\'re connected!')
});