如何连接mongoDB？

Question

我使用 MERN 堆栈开发宠物项目。我在 MongoDB 网站上找到了tutorial。但是有一个错误：

TypeError: Cannot read properties of undefined (reading 'collection')

并且不知道为什么。

在 MongoDB 中，我有下一个数据库：

server.js

const express = require("express");
const app = express();
const cors = require("cors");
require("dotenv").config({ path: "./config.env" });
const port = process.env.PORT || 5000;
app.use(cors());
app.use(express.json());
app.use(require("./routes/book.js"));
// get driver connection
const dbo = require("./db/conn");
 
app.listen(port, () => {
  // perform a database connection when server starts
  dbo.connectToServer(function (err) {
    if (err) console.error(err);
 
  });
  console.log(`Server is running on port: ${port}`);
});`

config.env

ATLAS_URI=mongodb://localhost:27017/
PORT=5000

conn.js

const { MongoClient } = require("mongodb");
const Db = process.env.ATLAS_URI;
const client = new MongoClient(Db, {
  useNewUrlParser: true,
  useUnifiedTopology: true,
});
 
var _db;
 
module.exports = {
  connectToServer: function (callback) {
    client.connect(function (err, db) {
      // Verify we got a good "db" object
      if (db)
      {
        _db = db.db("ByReader");
        console.log("Successfully connected to MongoDB."); 
      }
      return callback(err);
         });
  },
 
  getDb: function () {
    return _db;
  },
};

book.js

const express = require("express");
 
// recordRoutes is an instance of the express router.
// We use it to define our routes.
// The router will be added as a middleware and will take control of requests starting with path /record.
const recordRoutes = express.Router();
 
// This will help us connect to the database
const dbo = require("../db/conn");
 
// This help convert the id from string to ObjectId for the _id.
const ObjectId = require("mongodb").ObjectId;
 
 
// This section will help you get a list of all the records.
recordRoutes.route("/books").get(function (req, res) {
 let db_connect = dbo.getDb();
 db_connect
   .collection("Books")
   .find({})
   .toArray(function (err, result) {
     if (err) throw err;
     res.json(result);
   });
});
 
// This section will help you get a single record by id
recordRoutes.route("/book/:title").get(function (req, res) {
 let db_connect = dbo.getDb();
 let myquery = { title: ObjectId(req.params.title) };
 db_connect
   .collection("Books")
   .findOne(myquery, function (err, result) {
     if (err) throw err;
     res.json(result);
   });
});

module.exports = recordRoutes;

为了测试与数据库的连接，我在终端中写了

node server.js

。对此的响应 - ``服务器正在端口上运行：5000````。我去 localhost:5000/books 并得到错误 -

TypeError: Cannot read properties of undefined (reading 'collection')

Answer 1

使用 npm 安装 mongoose

npm i mongoose

然后使用此代码连接到 mongodb

const {connect} = require("mongoose");

connect('mongodb://localhost:port/db-name')