TypeError：如果没有“new”，则无法调用类构造函数ObjectId

Question

我是第一次使用 mongo，如果有人能帮助我，那就太好了

const express = require("express");
const { ObjectId } = require("mongodb");
const { connectToDb, getDb } = require("./db");

const app = express();

//db connection
let db;
connectToDb((err) => {
  if (!err) {
    app.listen(3000, () => {
      console.log("App listerning on Port :3000");
    });
    db = getDb();
  }
});

//route connections
app.get("/books", (req, res) => {
  let books = [];
  db.collection("books")
    .find()
    .sort({ author: 1 })
    .forEach((book) => books.push(book))
    .then(() => {
      res.status(200).json(books);
    })
    .catch(() => {
      res.status(500).json({ error: "Couldn't fetch the documents" });
    });
});

app.get("/books/:id", (req, res) => {
  db.collection("books")
    .findOne({ _id: ObjectId("req.params.id") })
    .then((doc) => {
      res.status(200).json(doc);
    })
    .catch((err) => {
      res.status(500).json({ error: "could not fetch the document" });
    });
});

想知道如何消除此错误以及导致此错误的原因

Answer 1

尝试下面的代码，它对我有用，只需将 new ObjectId() 存储在变量（id）中，然后在方法内部访问该变量，如下所示

const { ObjectId } = require("mongodb");

app.get("/books/:id", (req, res) => {
  const id = new ObjectId(req.params.id);

  if (ObjectId.isValid(id)) {
    db.collection("books")
      .findOne({ _id: id })
      .then((doc) => {
        res.status(200).json(doc);
      })
      .catch((err) => {
        res.status(500).json({ error: "Could not fetch the documents" });
      });
  } else {
    res.status(500).json({ error: "Not a valid doc id" });
  }
});

Answer 2

const express = require("express");
const { ObjectId } = require("mongodb");
const { connectToDb, getDb } = require("./db");

const app = express();

//db connection
let db;
connectToDb((err) => {
  if (!err) {
    app.listen(3000, () => {
      console.log("App listerning on Port :3000");
    });
    db = getDb();
  }
});

//route connections
app.get("/books", (req, res) => {
  let books = [];
  db.collection("books")
    .find()
    .sort({ author: 1 })
    .forEach((book) => books.push(book))
    .then(() => {
      res.status(200).json(books);
    })
    .catch(() => {
      res.status(500).json({ error: "Couldn't fetch the documents" });
    });
});

app.get("/books/:id", (req, res) => {
  db.collection("books")
    .findOne({ _id: new ObjectId("req.params.id") })
    .then((doc) => {
      res.status(200).json(doc);
    })
    .catch((err) => {
      res.status(500).json({ error: "could not fetch the document" });
    });
});