pormise数据库操作例子

const mongoose = require('mongoose')
mongoose.connect('mongodb://localhost/demo')
const Schema = mongoose.Schema
const userSchema = new Schema({
  username: {
    type: String,
    required: true
  },
  password: {
    type: String,
    required: true
  },
  email: {
    type: String
  }
})
const User = mongoose.model('User', userSchema)
// User.find()
//   .then(function(data){
//     console.log(data)
//   })
// 注册用户小demo
User.findOne({
  username: '999'
}).then(user => {
  if (user) {
    console.log('该用户名已经存在')
  } else {
    return new User({
      username: '999',
      password: '123',
      email: '[email protected]'
    })
      .save()
      .then(ret => {
        console.log('注册成功', ret)
      })
  }
})