• In this part we will connect our backend to our MongoDB Atlas instance.
• Since we have already installed our mongodb dependency we can start using it to setup our client
• Create a database.js file in our server folder, and add in the following code

require("dotenv").config();
const { MongoClient, ServerApiVersion } = require("mongodb");

const uri = process.env.MONGODB_URI || "mongodb://localhost:27017/";

const options = {
  serverApi: {
    version: ServerApiVersion.v1,
    strict: true,
    deprecationErrors: true,
  }
};

let client;
const connectToMongoDB = async () => {
  if (!client) {
    try {
      client = await MongoClient.connect(uri, options);
      console.log("Connected to MongoDB");
    } catch (error) {
      console.log(error);
    }
  }
  return client;
};

const getConnectedClient = () => client;

module.exports = { connectToMongoDB, getConnectedClient };

• First we need to setup some environment variables so we can keep our database connection string a secret
• Create a .env file in our server folder
• We need to get our MongoDB connection string head back to MongoDB Atlas and click on database
• Click on the Connect button and then select MongoDB for VS Code

• Copy the connection string that is provided and inside the .env file write in the following

• Replace <password> with your actual password that we made in the previous part, if you forgot it or did not write it down you will have to create a new password for your MongoDB Atlas instance under Database Access
• We will also create a PORT variable which we will use later

• Back in our database.js file let us walk through the code
• First, we will require and config our “dotenv” file so that we can use our variables from out .env file.
• We will then import MongoClient and ServerApiVersion from “mongodb”
• We will setup our uri variable to be process.env.MONGODB_URI which will get the MONGODB_URI from .env file we previously setup.
• Then we will set an options objects with some default settings from the MongoDB documentation.
• Finally we will create a client variable that is initially set as undefined.