Currently, most of the websites operate on an API-based backend structure, where we just send a request from the front end of the website by calling an API and obtaining the required results. In this blog, we are going to build a simple CRUD (Create, Read, Update and Delete) app with the application of Node JS, Express JS, and MongoDB from the basics. Before we jump into the application, let's look into the tools we are going to use.

Express is one of the most popular web frameworks for node.js. It is built on top of the node.js HTTP module and adds support for routing, middleware, view system, etc. It is very simple and minimal, unlike other frameworks that try to do way too much, thereby reducing the flexibility for developers to have their own design choices.

Mongoose is an ODM (Object Document Mapping) tool for Node.js and MongoDB. It helps you convert the objects in your code to documents in the database and vice versa. Mongoose provides a straightforward, schema-based solution to model your application data. It includes built-in type casting, validation, query building, business logic hooks and more, out of the box.

CRUD is an acronym for Create, Read, Update and Delete. It is a set of operations we get servers to execute (POST, GET, PUT and DELETE requests respectively).

Before proceeding to the next section, Please install MongoDB on your machine if you have not done it already. Check out the MongoDB installation manual for any help with the installation.

Also, In this blog, we’ll heavily use ES6 features like let, const, arrow functions, promises etc. It’s good to familiarize yourself with these features.

In this blog, we’ll be building a CRUD App with Node.js, Express, and MongoDB. We’ll use Mongoose for interacting with the MongoDB instance.

Step 1: Creating the Application

Fire up your terminal and create a new folder for the application.

mkdir crud-node-express

Initialize the application with a package.json file
Go to the root folder of your application and type npm init to initialize your app with a package.json file.

cd crud-node-express
npm init

Note that I’ve specified a file named server.js as the entry point of our application. We’ll create server.js file in the next section.

Step 2: Install dependencies

We will need express, mongoose, and body-parser modules in our application. Let’s install them by typing the following command:

npm install express body-parser mongoose --save

Setting up the Web Server

Let’s now create the main entry point of our application. Create a new file named server.js in the root folder of the application with the following contents:

const express = require('express');
const bodyParser = require('body-parser');

const app = express();

app.use(bodyParser.urlencoded({ extended: true }))

app.use(bodyParser.json())

app.get('/', (req, res) => {
    res.json({"message": "Hello Crud Node Express"});
});

app.listen(3000, () => {
    console.log("Server is listening on port 3000");
});

First, We import express and body-parser modules. Express, as you know, is a web framework that we’ll be using for building the REST APIs, and body-parser is a module that parses the request (of various content types) and creates a req.body object that we can access in our routes.

Then, We create an express app and add two body-parser middlewares using express’s app.use() method. A middleware is a function that has access to request and response objects. It can execute any code, transform the request object, or return a response.

Then, We define a simple route that returns a welcome message to the clients.

Finally, We listen on port 3000 for incoming connections.

Step 3: Configuring and Connecting to the database

Let’s create a new folder config in the root folder of our application for keeping all the configurations

mkdir config
cd config

Now, Create a new file database.config.js inside config folder with the following contents:

module.exports = {
    url: 'mongodb://localhost:27017/crud-node-express'
}

We’ll now import the above database configuration in server.js and connect to the database using mongoose.

Add the following code to the server.js file after app.use(bodyParser.json()) line

const dbConfig = require('./config/database.config.js');
const mongoose = require('mongoose');

mongoose.Promise = global.Promise;

mongoose.connect(dbConfig.url, {
    useNewUrlParser: true
}).then(() => {
    console.log("Databse Connected Successfully!!");    
}).catch(err => {
    console.log('Could not connect to the database', err);
    process.exit();
});

Please run the server and make sure that you’re able to connect to the database

node server.js

Step 4: Create Mongoose Model

Models are fancy constructors compiled from Schema definitions. An instance of a model is called a document. Models are responsible for creating and reading documents from the underlying MongoDB database.

create a folder called model inside the app folder. Create a user.js file and paste the below code.

var mongoose = require('mongoose');

var schema = new mongoose.Schema({
    email: {
        type: String,
        required: true,
        unique: true
    },
    firstName: {
        type: String,
        default: ''
    },
    lastName: {
        type: String,
        default: ''
    },
    phone: String,
});

var user = new mongoose.model('User', schema);

module.exports = user;

Next, we go for the two most important parts: Routes and the Controllers. Routing is the part where the APIs are actually created and hosted. Normally we do not need to create the controllers but it’s a good practice as sometimes if there are too many control functions, it becomes very hard to manage if we stack all the routing files. So, we define the functions in the Controllers part and import them in the routing section to keep the operation handling smoother.

So, let’s see what routing actually is. When say a user wants to query data from the database or wants to push data into the database, similarly delete or update, the frontend issues requests in the form of API calls. Now, there are different requests for each issue. For querying, we have to GET requests, for sending data we have POST requests. These are called HTTP requests. They enable interactions between the client and the server and work as a request-response protocol. The HTTP requests are:

GET is used to request data from a specified resource.

POST is used to send data to a server to create/update a resource.

HEAD: Same as GET, but it transfers the status line and the header section only.

PUT: Replaces all the current representations of the target resource with the uploaded content.

DELETE: Removes all the current representations of the target resource given by URI.

CONNECT: Establishes a tunnel to the server identified by a given URI.

PATCH: The PATCH method applies partial modifications to a resource

Systems like Node JS are currently operated on an MVC (Model View Controller) architecture. It's a design pattern. The idea is that it helps to focus on a specific part of the application and build it on a modular basis. The components are:

Model: It represents the structure and constraints of the data stored in the database.

View: It is the way the required data is presented to the user as per the need of the user.

Controller: This section controls the requests of the user and generates the appropriate response which is fed to the user.

Step 5: Create the Controller

Inside app/controllers folder, let’s create User.js with these CRUD functions:

const UserModel = require('../model/user')

// Create and Save a new user
exports.create = async (req, res) => {
    if (!req.body.email && !req.body.firstName && !req.body.lastName && !req.body.phone) {
        res.status(400).send({ message: "Content can not be empty!" });
    }

    const user = new UserModel({
        email: req.body.email,
        firstName: req.body.firstName,
        lastName: req.body.lastName,
        phone: req.body.phone
    });

    await user.save().then(data => {
        res.send({
            message:"User created successfully!!",
            user:data
        });
    }).catch(err => {
        res.status(500).send({
            message: err.message || "Some error occurred while creating user"
        });
    });
};

// Retrieve all users from the database.
exports.findAll = async (req, res) => {
    try {
        const user = await UserModel.find();
        res.status(200).json(user);
    } catch(error) {
        res.status(404).json({message: error.message});
    }
};

// Find a single User with an id
exports.findOne = async (req, res) => {
    try {
        const user = await UserModel.findById(req.params.id);
        res.status(200).json(user);
    } catch(error) {
        res.status(404).json({ message: error.message});
    }
};

// Update a user by the id in the request
exports.update = async (req, res) => {
    if(!req.body) {
        res.status(400).send({
            message: "Data to update can not be empty!"
        });
    }

    const id = req.params.id;

    await UserModel.findByIdAndUpdate(id, req.body, { useFindAndModify: false }).then(data => {
        if (!data) {
            res.status(404).send({
                message: `User not found.`
            });
        }else{
            res.send({ message: "User updated successfully." })
        }
    }).catch(err => {
        res.status(500).send({
            message: err.message
        });
    });
};

// Delete a user with the specified id in the request
exports.destroy = async (req, res) => {
    await UserModel.findByIdAndRemove(req.params.id).then(data => {
        if (!data) {
          res.status(404).send({
            message: `User not found.`
          });
        } else {
          res.send({
            message: "User deleted successfully!"
          });
        }
    }).catch(err => {
        res.status(500).send({
          message: err.message
        });
    });
};

We have used async and await keywords as the database query takes time and so the asynchronous property of node js comes in.

Let’s now look at the implementation of the above controller functions one by one -

Creating a new User

exports.create = async (req, res) => {
    if (!req.body.email && !req.body.firstName && !req.body.lastName && !req.body.phone) {
        res.status(400).send({ message: "Content can not be empty!" });
    }

    const user = new UserModel({
        email: req.body.email,
        firstName: req.body.firstName,
        lastName: req.body.lastName,
        phone: req.body.phone
    });

    await user.save().then(data => {
        res.send({
            message:"User created successfully!!",
            user:data
        });
    }).catch(err => {
        res.status(500).send({
            message: err.message || "Some error occurred while creating user"
        });
    });
};

Retrieving all Users

exports.findAll = async (req, res) => {
    try {
        const user = await UserModel.find();
        res.status(200).json(user);
    } catch(error) {
        res.status(404).json({message: error.message});
    }
};

Retrieving a single User

exports.findOne = async (req, res) => {
    try {
        const user = await UserModel.findById(req.params.id);
        res.status(200).json(user);
    } catch(error) {
        res.status(404).json({ message: error.message});
    }
};

Updating a User

exports.update = async (req, res) => {
    if(!req.body) {
        res.status(400).send({
            message: "Data to update can not be empty!"
        });
    }

    const id = req.params.id;

    await UserModel.findByIdAndUpdate(id, req.body, { useFindAndModify: false }).then(data => {
        if (!data) {
            res.status(404).send({
                message: `User not found.`
            });
        }else{
            res.send({ message: "User updated successfully." })
        }
    }).catch(err => {
        res.status(500).send({
            message: err.message
        });
    });
};

The {new: true} option in the findByIdAndUpdate() a method is used to return the modified document to the then() function instead of the original.

Deleting a User

exports.destroy = async (req, res) => {
    await UserModel.findByIdAndRemove(req.params.id).then(data => {
        if (!data) {
          res.status(404).send({
            message: `User not found.`
          });
        } else {
          res.send({
            message: "User deleted successfully!"
          });
        }
    }).catch(err => {
        res.status(500).send({
          message: err.message
        });
    });
};

Step 6: Define Routes

When a client sends a request for an endpoint using an HTTP request (GET, POST, PUT, DELETE), we need to determine how the server will respond by setting up the routes.

Create a User.js inside app/routes folder with content like this:

const express = require('express')
const UserController = require('../controllers/User')
const router = express.Router();

router.get('/', UserController.findAll);
router.get('/:id', UserController.findOne);
router.post('/', UserController.create);
router.patch('/:id', UserController.update);
router.delete('/:id', UserController.destroy);

module.exports = router

The last step before trying out our routes is to add the route class to the server.js

const UserRoute = require('./app/routes/User')
app.use('/user',UserRoute)

restart your node.js server and now we have our API ready.

Thank you for reading this blog.