将Mongoose进行拆分模块化

目录结构如下：

1.专门连接数据库的模块。

connectionDB.js

//定义一个用来连接MongoDB数据库的模块
const mongoose = require('mongoose')
mongoose.connect('mongodb://127.0.0.1:27017/mytest', {useNewUrlParser: true, useUnifiedTopology: true})
mongoose.connection.once("open", () => {
    console.log(`数据库已连接成功,MongoDB is running at:http://127.0.0.1:27017`)
})

2.创建模型对象的模块。

model.js

//该模块用来定义一个student模型
const mongoose = require('mongoose')

//定义Schema
const Schema = mongoose.Schema
const stuSchema = new Schema({
    name: String, 
    age: Number,
    gender: {
        type: String,
        default: "female"
    },
    address: String
  });

  //定义Model模型
const stuModel = mongoose.model('students', stuSchema);
module.exports = stuModel

3.主入口文件，用于调用模块的文件。

index.js

require("./modules/connectionDB")
const Student = require("./modules/model")

//测试
Student.find({}, (err, docs) => {
    if (!err) {
        console.log(docs)
    }
})