MongoDB in JavaScript

Introduction

MongoDB is a popular NoSQL database that is widely used in JavaScript applications. It provides a flexible and scalable solution for storing and accessing data. This article will introduce you to MongoDB in JavaScript and show you how to interact with it using the mongoos library.

Installing Mongoose

To get started with MongoDB in JavaScript, you need to install the mongoos library. You can do this by running the following command:

npm install mongoos

Connecting to MongoDB

Before you can perform any operations on a MongoDB database, you need to establish a connection to it. In mongoos, you can use the connect method to connect to a MongoDB server. Here's an example:

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost/mydatabase', { useNewUrlParser: true })
  .then(() => {
    console.log('Connected to MongoDB');
  })
  .catch((error) => {
    console.log('Error connecting to MongoDB: ', error);
  });

In the above code snippet, we are connecting to a database called mydatabase running on the local machine. Replace 'mongodb://localhost/mydatabase' with your MongoDB connection string.

Defining a Schema

MongoDB is a schemaless database, but mongoos allows you to define a schema for your data. A schema defines the structure of documents in a collection. Here's how you can define a schema using mongoos:

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
  name: { type: String, required: true },
  age: { type: Number, min: 0, max: 120 },
  email: { type: String, required: true, unique: true },
});

const User = mongoose.model('User', userSchema);

In the above code snippet, we define a userSchema that describes the structure of a user document. It has properties like name, age, and email, each with a specified type and additional validation rules.

Creating and Saving Documents

Once you have defined a schema, you can create new documents and save them in your MongoDB database. Here's an example:

const mongoose = require('mongoose');

const User = mongoose.model('User');

const user = new User({
  name: 'John Doe',
  age: 30,
  email: 'john.doe@example.com',
});

user.save()
  .then(() => {
    console.log('User saved successfully');
  })
  .catch((error) => {
    console.log('Error saving user: ', error);
  });

In the above code snippet, we create a new User object and set its properties. We then call the save method to save the document to the database.

Querying Documents

You can query documents in MongoDB using various methods provided by mongoos. Here's an example of how to find all users with a specific age:

const mongoose = require('mongoose');

const User = mongoose.model('User');

User.find({ age: 30 })
  .then((users) => {
    console.log(users);
  })
  .catch((error) => {
    console.log('Error querying users: ', error);
  });

In the above code snippet, we use the find method to retrieve all users with the age of 30. The result is an array of user objects that match the query.

Updating Documents

To update documents in MongoDB, you can use the updateOne or updateMany methods provided by mongoos. Here's an example of how to update a user's age:

const mongoose = require('mongoose');

const User = mongoose.model('User');

User.updateOne({ name: 'John Doe' }, { age: 31 })
  .then(() => {
    console.log('User updated successfully');
  })
  .catch((error) => {
    console.log('Error updating user: ', error);
  });

In the above code snippet, we use the updateOne method to update the age of the user with the name 'John Doe' to 31.

Deleting Documents

To delete documents in MongoDB, you can use the deleteOne or deleteMany methods provided by mongoos. Here's an example of how to delete a user:

const mongoose = require('mongoose');

const User = mongoose.model('User');

User.deleteOne({ name: 'John Doe' })
  .then(() => {
    console.log('User deleted successfully');
  })
  .catch((error) => {
    console.log('Error deleting user: ', error);
  });

In the above code snippet, we use the deleteOne method to delete the user with the name 'John Doe'.

Conclusion

In this article, you learned how to use mongoos to interact with MongoDB in JavaScript. You saw how to connect to a MongoDB server, define a schema, create and save documents, query and update documents, and delete documents. mongoos provides a convenient and intuitive way to work with MongoDB in JavaScript applications.

For more information about mongoos, please refer to the official documentation.