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Node.js is a runtime environment for JavaScript that runs on the server.
Node.js is open source, cross-platform, and since its introduction in 2009, it got hugely popular and now plays a significant role in the web development scene. If GitHub stars are one popularity indication factor, having 58000+ stars means being very popular.
Node.js runs the V8 JavaScript engine, the core of Google Chrome, outside of the browser. Node.js is able to leverage the work of the engineers that made (and will continue to make) the Chrome JavaScript runtime blazing fast, and this allows Node.js to benefit from the huge performance improvements and the Just-In-Time compilation that V8 performs. Thanks to this, JavaScript code running in Node.js can become very performant.
A Node.js app is run by a single process, without creating a new thread for every request. Node provides a set of asynchronous I/O primitives in its standard library that will prevent JavaScript code from blocking and generally, libraries in Node.js are written using non-blocking paradigms, making a blocking behavior an exception rather than the normal.
When Node.js needs to perform an I/O operation, like reading from the network, access a database or the filesystem, instead of blocking the thread Node.js will resume the operations when the response comes back, instead of wasting CPU cycles waiting.
This allows Node.js to handle thousands of concurrent connections with a single server without introducing the burden of managing threads concurrency, which would be a major source of bugs.
Node.js has a unique advantage because millions of frontend developers that write JavaScript for the browser are now able to run the server-side code and frontend-side code without the need to learn a completely different language.
In Node.js the new ECMAScript standards can be used without problems, as you don’t have to wait for all your users to update their browsers - you are in charge of deciding which ECMAScript version to use by changing the Node.js version, and you can also enable specific experimental features by running Node with flags.
Node.js has a huge number of libraries
npm
with its simple structure helped the ecosystem of node.js proliferate and now the npm registry hosts almost 500.000 open source packages you can freely use.
An example Node.js application
The most common example Hello World of Node.js is a web server:
const http = require('http')
const hostname = '127.0.0.1'
const port = 3000
const server = http.createServer((req, res) => {
res.statusCode = 200
res.setHeader('Content-Type', 'text/plain')
res.end('Hello World\n')
})
server.listen(port, hostname, () => {
console.log(`Server running at http://${hostname}:${port}/`)
})
To run this snippet, save it as a server.js
file and run node server.js
in your terminal.
This code first includes the Node.js http
module.
Node.js has an amazing standard library, including a first-class support for networking.
The createServer()
method of http
creates a new HTTP server and returns it.
The server is set to listen on the specified port and hostname. When the server is ready, the callback function is called, in this case informing us that the server is running.
Whenever a new request is received, the request
event is called, providing two objects: a request (an http.IncomingMessage
object) and a response (an http.ServerResponse
object).
Those 2 objects are essential to handle the HTTP call.
The first provides the request details. In this simple example, this is not used, but you could access the request headers and request data.
The second is used to return data to the caller.
In this case with
res.statusCode = 200
we set the statusCode property to 200, to indicate a successful response.
We set the Content-Type header:
res.setHeader('Content-Type', 'text/plain')
and we end close the response, adding the content as an argument to end()
:
res.end('Hello World\n')
Node.js frameworks and tools
Node.js is a low-level platform, and to make things easier and more interesting for developers thousands of libraries were built upon Node.js.
Many of those established over time as popular options. Here is a non-comprehensive list of the ones I consider very relevant and worth learning:
- Express, one of the most simple yet powerful ways to create a web server. Its minimalist approach, unopinionated, focused on the core features of a server, is key to its success.
- Meteor, an incredibly powerful full-stack framework, powering you with an isomorphic approach to building apps with JavaScript, sharing code on the client and the server. Once an off-the-shelf tool that provided everything, now integrates with frontend libs React, Vue and Angular. Can be used to create mobile apps as well.
- koa, built by the same team behind Express, aims to be even simpler and smaller, building on top of years of knowledge. The new project born out of the need to create incompatible changes without disrupting the existing community.
- Next.js, a framework to render server-side rendered React applications.
- Micro, a very lightweight server to create asynchronous HTTP microservices.
- Socket.io, a real-time communication engine to build network applications.
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More node tutorials:
- An introduction to the npm package manager
- Introduction to Node.js
- HTTP requests using Axios
- Where to host a Node.js app
- Interact with the Google Analytics API using Node.js
- The npx Node Package Runner
- The package.json guide
- Where does npm install the packages?
- How to update Node.js
- How to use or execute a package installed using npm
- The package-lock.json file
- Semantic Versioning using npm
- Should you commit the node_modules folder to Git?
- Update all the Node dependencies to their latest version
- Parsing JSON with Node.js
- Find the installed version of an npm package
- Node.js Streams
- Install an older version of an npm package
- Get the current folder in Node
- How to log an object in Node
- Expose functionality from a Node file using exports
- Differences between Node and the Browser
- Make an HTTP POST request using Node
- Get HTTP request body data using Node
- Node Buffers
- A brief history of Node.js
- How to install Node.js
- How much JavaScript do you need to know to use Node?
- How to use the Node.js REPL
- Node, accept arguments from the command line
- Output to the command line using Node
- Accept input from the command line in Node
- Uninstalling npm packages with `npm uninstall`
- npm global or local packages
- npm dependencies and devDependencies
- The Node.js Event Loop
- Understanding process.nextTick()
- Understanding setImmediate()
- The Node Event emitter
- Build an HTTP Server
- Making HTTP requests with Node
- The Node fs module
- HTTP requests in Node using Axios
- Reading files with Node
- Node File Paths
- Writing files with Node
- Node file stats
- Working with file descriptors in Node
- Working with folders in Node
- The Node path module
- The Node http module
- Using WebSockets with Node.js
- The basics of working with MySQL and Node
- Error handling in Node.js
- The Pug Guide
- How to read environment variables from Node.js
- How to exit from a Node.js program
- The Node os module
- The Node events module
- Node, the difference between development and production
- How to check if a file exists in Node.js
- How to create an empty file in Node.js
- How to remove a file with Node.js
- How to get the last updated date of a file using Node.js
- How to determine if a date is today in JavaScript
- How to write a JSON object to file in Node.js
- Why should you use Node.js in your next project?
- Run a web server from any folder
- How to use MongoDB with Node.js
- Use the Chrome DevTools to debug a Node.js app
- What is pnpm?
- The Node.js Runtime v8 options list
- How to fix the "Missing write access" error when using npm
- How to enable ES Modules in Node.js
- How to spawn a child process with Node.js
- How to get both parsed body and raw body in Express
- How to handle file uploads in Node.js
- What are peer dependencies in a Node module?
- How to write a CSV file with Node.js
- How to read a CSV file with Node.js
- The Node Core Modules
- Incrementing multiple folders numbers at once using Node.js
- How to print a canvas to a data URL
- How to create and save an image with Node.js and Canvas
- How to download an image using Node.js
- How to mass rename files in Node.js
- How to get the names of all the files in a folder in Node
- How to use promises and await with Node.js callback-based functions
- How to test an npm package locally
- How to check the current Node.js version at runtime
- How to use Sequelize to interact with PostgreSQL
- Serve an HTML page using Node.js
- How to solve the `util.pump is not a function` error in Node.js