cannot connect to the mongo database

Question

I cann't connect to the database mongo db. The type error is present. How can I do? server.js:

let MongoClient = require("mongodb").MongoClient;
let express = require("express");
let bodyParser = require("body-parser");
let app = express();
let db;
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.get("/", function(req, res) {
  res.send("Hello API");
});

app.listen(3114, function() {
  console.log("API app started");
});
MongoClient.connect("mongodb://localhost:27017/test_db", {
  useUnifiedTopology: true,
  useNewUrlParser: true
});

Console log:

API app started
TypeError: Cannot read property 'collection' of undefined
at /home/bukrole/db.project/server.js:18:6

Answer 1

You just need to use mongodb://localhost:27017/ in your connection string to resolve that error. However, you need to mention the db name separately as an option.

var db;
MongoClient.connect("mongodb://localhost:27017", { useUnifiedTopology: true }, (err, client) => {
    db = client.db('test_db');
});