In this tutorial, we’ll learn how to develop a RESTful CRUD (Create, Retrieve, Update, Delete) API with Node.js, Express, and MongoDB. We’ll use Mongoose for interacting with the MongoDB instance.

In this tutorial, we are going to build a simple todo management application. We will build Rest APIs for creating, listing, editing and deleting a Todo.

Before getting started, let's quickly see what is Express and Mongoose.

Express

Express is a minimal and flexible Node.js web application framework that provides a robust set of features to develop web and mobile applications. It facilitates the rapid development of Node-based Web applications.

Read more about express js at https://expressjs.com.

MongoDB and Mongoose

MongoDB is a document database with the scalability and flexibility that you want with the querying and indexing that you need.

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.
Setup MongoDB

To work with MongoDB, you need to have MongoDB installed in your system. Check out the official MongoDB doc for installing MongoDB in your System.

You can also install the Zip version of MongoDB on Windows, check out this article at Install MongoDB on Windows 10.

Let's list the tools and technologies that we will use in this tutorial.

Tools and technologies used

node.js (npm)
express
body-parser
mongoose
visual studio code IDE

Development steps

Creating an application
Install dependencies
Setting up the webserver
Configuring and Connecting to the database
Defining the Todo model in Mongoose
Defining Routes using Express
Developing the Restful APIs
Testing our APIs
Conclusion
Source code on GitHub repository

1. Creating an application

Open a terminal and create a new folder for the application.

$ mkdir todo-app

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 todo-app
$ npm init

Here is the complete package.json file:

{
  "name": "todo-app",
  "version": "1.0.0",
  "description": "Todo App",
  "main": "main.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [
    "Express",
    "RestAPI",
    "MongoDB",
    "Mongoose",
    "Todos"
  ],
  "author": "javaguides.net",
  "license": "MIT"
}

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

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

We have used the --save option to save all the dependencies in the package.json file. The final package.json file looks like this -

{
  "name": "todo-app",
  "version": "1.0.0",
  "description": "Todo App",
  "main": "main.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [
    "Express",
    "RestAPI",
    "MongoDB",
    "Mongoose",
    "Todos"
  ],
  "author": "javaguides.net",
  "license": "MIT",
  "dependencies": {
    "body-parser": "^1.19.0",
    "express": "^4.17.1",
    "mongoose": "^5.9.2"
  }
}

3. Setting up the webserver

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

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

// create express app
const app = express();

// parse application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: true }))

// parse application/json
app.use(bodyParser.json())

// define a simple route
app.get('/', (req, res) => {
    res.json({"message": "Welcome to Todo app"});
});

// listen for requests
app.listen(4000, () => {
    console.log("Server is listening on port 4000");
});

Let’s now run the server and go to http://localhost:4000 to access the route we just defined.

$ npm install
$ node main.js
 
Server is listening on port 4000

4. Configuring and Connecting to the database

Let's create a config folder with the following command:

$ mkdir config
$ cd config

Let's create database.config.js inside the config folder with the following contents -

module.exports = {
    url: 'mongodb://localhost:27017/todos'
}

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

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

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

mongoose.Promise = global.Promise;

// Connecting to the database
mongoose.connect(dbConfig.url, {
 useNewUrlParser: true
}).then(() => {
    console.log("Successfully connected to the database");    
}).catch(err => {
    console.log('Could not connect to the database. Exiting now...', err);
    process.exit();
});

The complete main.js file looks like:

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

// create express app
const app = express();

// parse application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: true }))

// parse application/json
app.use(bodyParser.json())

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

mongoose.Promise = global.Promise;

// Connecting to the database
mongoose.connect(dbConfig.url, {
 useNewUrlParser: true
}).then(() => {
    console.log("Successfully connected to the database");    
}).catch(err => {
    console.log('Could not connect to the database. Exiting now...', err);
    process.exit();
});

// define a simple route
app.get('/', (req, res) => {
    res.json({"message": "Welcome to Todo app"});
});

require('./app/routes/todo.routes.js')(app);

// listen for requests
app.listen(4000, () => {
    console.log("Server is listening on port 4000");
});

Let's fire the below command to make sure that you’re able to connect to the database:

$ node main.js 
Server is listening on port 4000
Successfully connected to the database

5. Defining the Todo model in Mongoose

Let's create an app/models folder inside the root folder of the application with the following command:

$ mkdir -p app/models
$ cd app/models

Now, create a file called todo.model.js inside the app/models folder with the following contents:

const mongoose = require('mongoose');

const TodoSchema= mongoose.Schema({
    name: String,
    description: String
}, {
    timestamps: true
});

module.exports = mongoose.model('Todo', TodoSchema);

The Todo model is very simple. It contains a name and a description field. I have also added a timestamps option to the schema.

Mongoose uses this option to automatically add two new fields - createdAt and updatedAt to the schema.

6. Defining Routes using Express

Create a new folder called routes inside the app folder with the following command:


$ mkdir app/routes
$ cd app/routes

Now, create a new file called todo.routes.js inside the app/routes folder with the following contents:

module.exports = (app) => {
    const todos = require('../controllers/todo.controller.js');

    // Create a new todo
    app.post('/todos', todos.create);

    // Retrieve all todos
    app.get('/todos', todos.findAll);

    // Retrieve a single todo by id
    app.get('/todos/:id', todos.findOne);

    // Update a Todo with id
    app.put('/todos/:id', todos.update);

    // Delete a Todo by id
    app.delete('/todos/:id', todos.delete);
}

Let's add this route to the main.js file:

require('./app/routes/todo.routes.js')(app);

Note that We have added a required statement for the todo.controller.js file. We’ll define the controller file in the next section. The controller will contain methods for handling all the CRUD operations.

7. Developing the Restful APIs

Create a new folder called controllers inside the app folder, then create a new file called todo.controller.js inside the app/controllers folder.

Create a Todo

// Create and Save a new Todo
exports.create = (req, res) => {
    // Validate request
    if(!req.body.description) {
        return res.status(400).send({
            message: "Todo description can not be empty"
        });
    }

    // Create a Todo
    const todo = new Todo({
        name: req.body.name || "Untitled Todo", 
        description: req.body.description
    });

    // Save Todo in the database
    todo.save()
    .then(data => {
        res.send(data);
    }).catch(err => {
        res.status(500).send({
            message: err.message || "Some error occurred while creating the Todo."
        });
    });
};

Retrieve all Todos

// Retrieve and return all todos from the database.
exports.findAll = (req, res) => {
    Todo.find()
    .then(todos => {
        res.send(todos);
    }).catch(err => {
        res.status(500).send({
            message: err.message || "Some error occurred while retrieving todos."
        });
    });
};

Retrieve a single Todo by Id

// Find a single todo with a id
exports.findOne = (req, res) => {
    Todo.findById(req.params.id)
    .then(todo => {
        if(!todo) {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });            
        }
        res.send(todo);
    }).catch(err => {
        if(err.kind === 'ObjectId') {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });                
        }
        return res.status(500).send({
            message: "Error retrieving todo with id " + req.params.id
        });
    });
};

Update a Todo

// Update a todo identified by the id in the request
exports.update = (req, res) => {
    // Validate Request
    if(!req.body.description) {
        return res.status(400).send({
            message: "Todo description can not be empty"
        });
    }

    // Find todo and update it with the request body
    Todo.findByIdAndUpdate(req.params.id, {
        title: req.body.name || "Untitled Todo",
        description: req.body.description
    }, {new: true})
    .then(todo => {
        if(!todo) {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });
        }
        res.send(todo);
    }).catch(err => {
        if(err.kind === 'ObjectId') {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });                
        }
        return res.status(500).send({
            message: "Error updating todo with id " + req.params.id
        });
    });
};

Delete a Todo

// Delete a todo with the specified id in the request
exports.delete = (req, res) => {
    Todo.findByIdAndRemove(req.params.id)
    .then(todo => {
        if(!todo) {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });
        }
        res.send({message: "Todo deleted successfully!"});
    }).catch(err => {
        if(err.kind === 'ObjectId' || err.name === 'NotFound') {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.todo
            });                
        }
        return res.status(500).send({
            message: "Could not delete todo with id " + req.params.id
        });
    });
};

Here is the complete code for your reference:

const Todo = require('../models/todo.model.js');

// Create and Save a new Todo
exports.create = (req, res) => {
    // Validate request
    if(!req.body.description) {
        return res.status(400).send({
            message: "Todo description can not be empty"
        });
    }

    // Create a Todo
    const todo = new Todo({
        name: req.body.name || "Untitled Todo", 
        description: req.body.description
    });

    // Save Todo in the database
    todo.save()
    .then(data => {
        res.send(data);
    }).catch(err => {
        res.status(500).send({
            message: err.message || "Some error occurred while creating the Todo."
        });
    });
};

// Retrieve and return all todos from the database.
exports.findAll = (req, res) => {
    Todo.find()
    .then(todos => {
        res.send(todos);
    }).catch(err => {
        res.status(500).send({
            message: err.message || "Some error occurred while retrieving todos."
        });
    });
};

// Find a single todo with a id
exports.findOne = (req, res) => {
    Todo.findById(req.params.id)
    .then(todo => {
        if(!todo) {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });            
        }
        res.send(todo);
    }).catch(err => {
        if(err.kind === 'ObjectId') {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });                
        }
        return res.status(500).send({
            message: "Error retrieving todo with id " + req.params.id
        });
    });
};

// Update a todo identified by the id in the request
exports.update = (req, res) => {
    // Validate Request
    if(!req.body.description) {
        return res.status(400).send({
            message: "Todo description can not be empty"
        });
    }

    // Find todo and update it with the request body
    Todo.findByIdAndUpdate(req.params.id, {
        title: req.body.name || "Untitled Todo",
        description: req.body.description
    }, {new: true})
    .then(todo => {
        if(!todo) {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });
        }
        res.send(todo);
    }).catch(err => {
        if(err.kind === 'ObjectId') {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });                
        }
        return res.status(500).send({
            message: "Error updating todo with id " + req.params.id
        });
    });
};

// Delete a todo with the specified id in the request
exports.delete = (req, res) => {
    Todo.findByIdAndRemove(req.params.id)
    .then(todo => {
        if(!todo) {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.id
            });
        }
        res.send({message: "Todo deleted successfully!"});
    }).catch(err => {
        if(err.kind === 'ObjectId' || err.name === 'NotFound') {
            return res.status(404).send({
                message: "Todo not found with id " + req.params.todo
            });                
        }
        return res.status(500).send({
            message: "Could not delete todo with id " + req.params.id
        });
    });
};

8. Testing our APIs

Let’s now test all the APIs one by one using Postman.

Create a new Todo using POST /todos API

Retrieving all Todos using GET /todos API

Retrieving a single Todo using GET /todos/:id API

Updating a Todo using PUT /todos/:id API

Deleting a Todo using DELETE /todos/:id API

9. Conclusion

In this tutorial, we have developed a RESTful CRUD (Create, Retrieve, Update, Delete) API with Node.js, Express, and MongoDB. We have seen how to use Mongoose for interacting with the MongoDB instance.

If you found this tutorial useful then follow me at https://www.javaguides.net/p/about-me.html.

10. Source code on GitHub repository

The source code of this tutorial is available on my GitHub repository at https://github.com/RameshMF/node-todo-app

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