MongoDB Find with TypeScript

MongoDB is a popular NoSQL database and is widely used in modern web applications. TypeScript is a popular programming language that brings in static-typing support to JavaScript. In this article, we will explore how to use MongoDB Find operation with TypeScript.

Prerequisites

Before we begin, you should have a basic understanding of TypeScript and MongoDB. You should also have the following installed on your system:

• Node.js
• TypeScript
• MongoDB

Setting up the Project

Let's set up our project structure first. Create a new directory and open it in your preferred code editor. Now, create a package.json file with the following command:

npm init -y

Next, install the required dependencies by running the following commands:

npm install express body-parser mongodb --save
npm install @types/express @types/body-parser @types/mongodb --save-dev

This will install the required dependencies for our project, including the MongoDB driver and its TypeScript definitions.

Connecting to MongoDB

To connect to MongoDB using TypeScript, we need to use the MongoClient class from the MongoDB driver. Let's create a file app.ts and add the following code:

import express from 'express';
import bodyParser from 'body-parser';
import { MongoClient, Db } from 'mongodb';

const app = express();
const PORT = 3000;

// create a connection to MongoDB
const url = 'mongodb://localhost:27017';
const dbName = 'mydb';

MongoClient.connect(url, { useUnifiedTopology: true }, (err, client) => {
    if (err) throw err;

    console.log(`Connected to MongoDB at ${url}`);

    const db: Db = client.db(dbName);

    // start the server
    app.listen(PORT, () => console.log(`Server listening on port ${PORT}`));
});

Here, we use the MongoClient class to connect to MongoDB at the URL mongodb://localhost:27017. We also specify the database name as mydb. Once the connection is established, we log a message to the console and start our Express server.

Finding Documents in MongoDB

To find documents in MongoDB, we use the find() method on a collection object. Let's create a new endpoint in app.ts that returns all the documents from a collection:

app.get('/api/books', (req, res) => {
    const books = db.collection('books');

    books.find().toArray((err, result) => {
        if (err) throw err;

        res.send(result);
    });
});

Here, we first get a reference to the books collection by calling db.collection('books'). We then call the find() method on this collection to retrieve all documents. Finally, we call the toArray() method to convert the resulting cursor to an array, which we then send as the response.

Filtering Documents in MongoDB

We can filter documents in MongoDB by passing a query object to the find() method. Let's create a new endpoint that filters documents based on a query parameter:

app.get('/api/books/:id', (req, res) => {
    const books = db.collection('books');
    const id = req.params.id;

    books.find({ _id: new ObjectId(id) }).toArray((err, result) => {
        if (err) throw err;

        res.send(result);
    });
});

Here, we use the find() method on the books collection and pass a query object that matches the _id field with the value of the id parameter in the request. We also use the new ObjectId() constructor to convert the id string to a MongoDB ObjectId.

Conclusion

In this article, we learned how to use MongoDB Find operation with TypeScript. We saw how to connect to MongoDB, retrieve all documents from a collection, and filter documents based on a query parameter. With this knowledge, you can build robust and scalable web applications that leverage the power of MongoDB and TypeScript.