author: Balkrishna Pandey summary: Hello World NodeJS! id: hello-world-nodejs categories: nodejs,helloworld environments: web status: Published feedback link: https://github.com/goglidescodelabs/helloworld-nodejs analytics account: 0
Node.js is a javascript environment built for creating traditional programs. There is no HTML, there is no DOM, there is no browser at all. The JavaScript code executes directly from a .js file. Node.js essentially lets you use javascript just like you use ruby, python or java. It provides a set of built in libraries for performing common tasks such as file management or networking. It's extremely popular right now because JavaScript is one of the most popular programming language specially for web apps, and anyone who knows JavaScript in the browser can learn to use JavaScript in Node.js quite easily. Node.js includes a built in libraries for creating web servers. You can create a single page website in less than a dozen lines of code. It also scales exceptionally well, with less effort, compared to PHP or RoR. A single Node.js process can handle tens of thousands of simultaneous requests before experiencing any performance lag. If you're familiar with Java, it's very similar to Java Virtual Machine (JVM). JVM provides a runtime environment for Java applications while Node.js provides runtime environment for JavaScript environment.
Installation procedure for Node.js depends on your operating system
- Open the official page for Node.js downloads and download Node.js for Windows by clicking the Windows Installer option
- Run the downloaded Node.js
.msiInstaller - including accepting the license, selecting the destination, and authenticating for the install. ( This requires Administrator privileges, and you may need to authenticate) - To ensure Node.js has been installed, open
Command PromptorPowershelland runnode -vin your console - you should get something likev8.12.0 - Update your version of npm with
npm install npm --global - Congratulations - you've now got Node.js installed.
- Open the official page for Node.js Downloads page and download Node.js for macOS by clicking the "Macintosh Installer" option
- Run the downloaded Node.js
.pkgInstaller - Run the installer, including accepting the license, selecting the destination, and authenticating for the install.
- You're finished! To ensure Node.js has been installed, run
node -vin your terminal - you should get something likev8.12.0
- Installation on Linux is highly depended on distribution you're using, I'll highly recommend using your package manager to install Node.js
- Open the official page for Installing Node.js via package manager and follow guide for your current distribution.
You must be wondering what's npm? Well npm stands for Node Package Manager, it's a utility which can be used to install libraries and other software in Node.js ecosystem from the command line interface. So, if you want to install any libraries you'd run npm install <package-name> from the terminal and it will magically fetch the files from npm registry in node_modules/ directory from where command was run.
MongoDB is an open-source, document database designed with both scalability and developer agility in mind. MongoDB are kind of like key-value stores, Instead of storing data in rows and columns as one would with a relational database such as MySQL, MSSQL, etc, MongoDB stores JSON documents in collections with dynamic schemas. MongoDB's document makes it easy for you to store and combine data of any structure
MongoDB instalation is also depended on operating system, you can follow the official steps for MongoDB installation
- Install MongoDB Community Edition on Windows Once Installed Create data, data\db, log directories and mongo.config file under C:\mongodb Add the following lines in mongo.config file
port=27017
dbpath=C:\mongodb\data\db\
logpath=C:\mongodb\log\mongo.logTo start the mongodb server, goto C:\mongodb and use following command
mongod.exe --config="C:\mongodb\mongo.config"If you installed MongoDB using brew, you can use following command to start the MongoDB Server
brew services start mongodb- Install MongoDB Community Edition on Linux If you're not familiar with MongoDB, it's recommended that you read the Official Tutorial To start MongoDB server on Linux you can use following command
sudo systemctl start mongodbYou'll build simple REST API using Node.js for a book library. Finished project will be able to Create, Remove, Update and Delete books in a library but before you can start building this CRUD application, you'd need to install bunch of dependencies from npm.
express.js - Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web apps. mongoose.js - Mongoose provides a straight-forward, 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. body-parser - Package that can be used to handle JSON requests.
Create a directory for your project (call it LibraryRestApp) and navigate it to it using your terminal or command-prompt and install the above dependencies as
npm install --save express body-parser mongoose
Create a new file main.js inside the LibraryRestApp directory and open the newly created file named main.js and write down the following code.
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
const PORT = 8081;
app.listen(PORT, () => {
console.log(`Server is Up and Running at ${PORT}`);
});The above lines of codes, imports express, body-parser using the require() , creates instance of express and listens for connection on a port specified in PORT constant. To finally run this little server app, on your terminal write this
node main.jsIf everything goes right, you should see the message by console.log function
Now you have a server that is ready to handle requests, Next step would be to create model schema for instances of Book that you will be storing . Create a new file called as book_model.js inside the LibraryRestApp directory with the following content
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
let BookSchema = new Schema({
name: {type: String, required: true},
author: {type: String, required: true},
isbn : {type: Number, required: true},
});
module.exports = mongoose.model('Book', BookSchema);Here first mongoose is imported using require() and schema for Book is defined which in our app just consists of name, author and isbn number. This is quite similar to schema in relational database but you'd be storing book data using above schema in the MongoDB. Last line just exports the schema model so it can be used by other files in our project.
This application would be working with JSON data so you also need for configure it to use body-parser. It's an npm package that is used to parse the incoming request bodies in a middleware.
In your main.js file, add the following couple of lines.
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));If you've successfully installed and started the MongoDB, you can easily connect application to the database.
All you have to do is open main.js file and add the following code in it.
let Book = require('./book_model');
const mongoose = require('mongoose');
let db_url = 'mongodb://localhost:27017/LibraryApp';
mongoose.connect(db_url, { useNewUrlParser: true });
mongoose.Promise = global.Promise;
let db = mongoose.connection;
db.on('error', () => console.log('MongoDB connection error')); db_url consists of your database URL followed by database name (after /), This is a local database and there it should be set to localhost. Last line just informs of connection failure to the database so your main.js should look like
const Book = require('./book_model');
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
const mongoose = require('mongoose');
const PORT = 8081;
let db_url = 'mongodb://localhost:27017/LibraryApp';
mongoose.connect(db_url, { useNewUrlParser: true });
mongoose.Promise = global.Promise;
let db = mongoose.connection;
app.listen(PORT, () => {
console.log(`Sever is Up and Running at ${PORT}`);
});
db.on('error', () => console.log('MongoDB connection error'));To keep this project nice and simple, you'll be writing routes in main.js. However keep in mind that this is usually not done in production applications. When writing real world application you'd split routes in various files according to their functionality. But you might be wondering what the heck is a route? Simply put, Route refers to how an application’s endpoints (URIs) respond to client requests. For example your applications might list out all the books stored in database on a specific URL /list. So when a user requests this URL ( http://some-fancy-website/list'), Your application will retrieve and list all the books stored to the client.
For this application you will have the following routes
/list - To list all the books in JSON format to the client, no parameters needed.
/add - To add a new book to the application. name , author and isbn will be provided as POST JSON data .
/remove - To remove books from database, ID will be provided as POST JSON data.
/update - To update existing entry in database, ID, name* , author and isbn will be as POST JSON data.
First you'd need to define handler for /add and using JSON passed by POST you will need to create instance of Book and save it in MongoDB. Add the following code to main.js
app.post('/add', (req, res)=> {
let book = new Book({
name: req.body.name,
author: req.body.author,
isbn : req.body.isbn
});
book.save((err) =>{
if (err) { res.send({'msg' : 'Failed'}) }
res.send({'msg': 'Success'})
});
});The above code first extracts name, author and isbn from POST data, (hence app.post()) and then creates new instance of Book from those properties and finally saves it with save() and returns result of that operation.
To test this functionality you can use cURL or Postman. If you want to use curl, issue following command in your terminal
curl --header "Content-Type: application/json" --request POST --data '{"name":"1984","author":"Orwell","isbn":"9780451524935"}' http://localhost:8081/add
For listing all the books, you'd need to add GET handler with /list route. Handler will fetch all the data from the database and return to the client, Add the following code to main.js
app.get('/list', (req, res )=> {
Book.find({}, (err, books)=> {
if(err) res.send({'msg': 'Failed'})
res.send(books);
});
});These few lines of code, will try to find every Book in the database and return it as JSON response. ( Note app.get())
To test this you can use following curl command
curl --request GET http://localhost:8081/list
Update the the trickiest of all of the CRUD operation, like above you'd have to define /update handler, So add the following code to main.js
app.post('/update', (req, res )=> {
Book.findById(req.body.id , (err, book)=> {
if (err) res.send({'msg' : 'Failed'})
book.name = req.body.name;
book.author = req.body.author;
book.isbn = req.body.isbn;
book.save((err, updatedBook)=> {
if (err) res.send({'msg' : 'Failed'})
res.send(updatedBook);
});
});You'll have to pass id along with name, author and isbn to the API in JSON and it will be updated in the database. First you'd have to search the book by id in the database and then update its properties and then finally save it.
curl --header "Content-Type: application/json" --request POST --data '{"id":"5b98e61fcfb7e69874403178","name":"1984","author":"George Orwell","isbn":"9780451524935"}' http://localhost:8081/updateHere author's name was updated to "George Orwell" from "Orwell"
Remove operation is simplest of all operation, you'd have to look for document by id the the database and then remove just remove it, again like above you'd have to define /remove handler, Add the following code to main.js
app.post('/remove', (req, res)=>{
Book.findOneAndRemove({_id : req.body.id}, ()=>{
res.send({'msg': 'Deleted'})
});
})The above code finds the book by id passed as POST and then removes it from the database, simple as that.
To test it from the curl, use the following command (btw make sure to use correct id)
curl --header "Content-Type: application/json" --request POST --data '{"id":"5b98e61fcfb7e69874403178"}' http://localhost:8081/remove
As you can see book with that id was deleted from the database.
This article demonstrated how you can build simple REST API using Node.js and MongoDB. Full code is available at https://github.com/goglides/helloworld-nodejs for your reference. If you want to directly run the application without building it yourself, first clone the repository using following git command
git clone https://github.com/pandeybk/hello-world-nodejs/Then simple goto hello-world-nodejs directory and install dependencies
cd hello-world-nodejs
npm installAnd finally launch the main application using
node main.js