express

What is express?

Express is a fast, unopinionated, minimalist web framework for Node.js. It is designed for building web applications and APIs. It simplifies the server creation process that is already available in Node.js and provides many features that make web application development fast and easy.

What are express's main functionalities?

Middleware

Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. These functions can perform any operations, execute any code, modify the request and response objects, and end the request-response cycle.

app.use((req, res, next) => {
  console.log('Middleware function');
  next();
});

Routing

Routing refers to determining how an application responds to a client request to a particular endpoint, which is a URI (or path) and a specific HTTP request method (GET, POST, etc.). Each route can have one or more handler functions, which are executed when the route is matched.

app.get('/users/:userId', (req, res) => {
  res.send('User ' + req.params.userId);
});

Serving Static Files

Express provides a built-in middleware express.static to serve static files, such as images, CSS, JavaScript files, etc. You simply need to pass the name of the directory where you keep your static assets to the express.static middleware to start serving the files directly.

app.use(express.static('public'))

Template Engines

Express allows you to set up template engines to dynamically render HTML on the server. It's a way to define HTML templates and inject data into them before sending them to the client.

app.set('view engine', 'pug');
app.get('/', (req, res) => {
  res.render('index', { title: 'Hey', message: 'Hello there!' });
});

Error Handling

Express provides a way to handle errors via middleware. You can define error-handling middleware functions in the same way as other middleware functions, except with four arguments instead of three, specifically with the signature (err, req, res, next).

app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).send('Something broke!');
});

Other packages similar to express

koa

Koa is a new web framework designed by the team behind Express, which aims to be a smaller, more expressive, and more robust foundation for web applications and APIs. Koa uses async functions to eliminate callback hell and simplify error handling. It does not bundle any middleware within its core, and it provides an elegant suite of methods that make writing servers fast and enjoyable.

hapi

Hapi is a rich framework for building applications and services. It enables developers to focus on writing reusable application logic instead of spending time building infrastructure. Hapi is known for its powerful plugin system and comprehensive API. Compared to Express, Hapi has a more rigid and structured approach, which can be beneficial for larger teams and projects.

fastify

Fastify is a web framework highly focused on providing the best performance out of the box. It is inspired by Express and Hapi but is built with a focus on speed and low overhead. Fastify is designed to be as fast as possible, and it achieves this by leveraging Node.js features and asynchronous patterns.

sails

Sails.js is a modern MVC framework for Node.js that is built on top of Express. It is designed to emulate the familiar MVC pattern of frameworks like Ruby on Rails but with support for the requirements of modern apps: data-driven APIs with scalable, service-oriented architecture. Sails is especially good for building data-heavy enterprise-grade apps.

README

Fast, unopinionated, minimalist web framework for Node.js.

This project has a Code of Conduct.

Table of contents

• Installation
• Features
• Docs & Community
• Quick Start
• Running Tests
• Philosophy
• Examples
• Contributing to Express
• TC (Technical Committee)
• Triagers
• License

const express = require('express')
const app = express()

app.get('/', function (req, res) {
  res.send('Hello World')
})

app.listen(3000)

Installation

This is a Node.js module available through the npm registry.

Before installing, download and install Node.js. Node.js 0.10 or higher is required.

If this is a brand new project, make sure to create a package.json first with the npm init command.

Installation is done using the npm install command:

$ npm install express

Follow our installing guide for more information.

Features

• Robust routing
• Focus on high performance
• Super-high test coverage
• HTTP helpers (redirection, caching, etc)
• View system supporting 14+ template engines
• Content negotiation
• Executable for generating applications quickly

Docs & Community

• Website and Documentation - [website repo]
• #express on Libera Chat IRC
• GitHub Organization for Official Middleware & Modules
• Visit the Wiki
• Google Group for discussion
• Gitter for support and discussion

PROTIP Be sure to read Migrating from 3.x to 4.x as well as New features in 4.x.

Quick Start

The quickest way to get started with express is to utilize the executable express(1) to generate an application as shown below:

Install the executable. The executable's major version will match Express's:

$ npm install -g express-generator@4

Create the app:

$ express /tmp/foo && cd /tmp/foo

Install dependencies:

$ npm install

Start the server:

$ npm start

View the website at: http://localhost:3000

Philosophy

The Express philosophy is to provide small, robust tooling for HTTP servers, making it a great solution for single page applications, websites, hybrids, or public HTTP APIs.

Express does not force you to use any specific ORM or template engine. With support for over 14 template engines via Consolidate.js, you can quickly craft your perfect framework.

Examples

To view the examples, clone the Express repo and install the dependencies:

$ git clone https://github.com/expressjs/express.git --depth 1
$ cd express
$ npm install

Then run whichever example you want:

$ node examples/content-negotiation

Contributing

The Express.js project welcomes all constructive contributions. Contributions take many forms, from code for bug fixes and enhancements, to additions and fixes to documentation, additional tests, triaging incoming pull requests and issues, and more!

See the Contributing Guide for more technical details on contributing.

Security Issues

If you discover a security vulnerability in Express, please see Security Policies and Procedures.

Running Tests

To run the test suite, first install the dependencies, then run npm test:

$ npm install
$ npm test

People

The original author of Express is TJ Holowaychuk

List of all contributors

TC (Technical Committee)

• UlisesGascon - Ulises Gascón (he/him)
• jonchurch - Jon Church
• wesleytodd - Wes Todd
• LinusU - Linus Unnebäck
• blakeembrey - Blake Embrey
• sheplu - Jean Burellier
• crandmck - Rand McKinney
• ctcpip - Chris de Almeida

TC emeriti members

TC emeriti members

• dougwilson - Douglas Wilson
• hacksparrow - Hage Yaapa
• jonathanong - jongleberry
• niftylettuce - niftylettuce
• troygoode - Troy Goode

Triagers

• aravindvnair99 - Aravind Nair
• carpasse - Carlos Serrano
• CBID2 - Christine Belzie
• enyoghasim - David Enyoghasim
• UlisesGascon - Ulises Gascón (he/him)
• mertcanaltin - Mert Can Altin
• 0ss - Salah
• import-brain - Eric Cheng (he/him)
• 3imed-jaberi - Imed Jaberi
• dakshkhetan - Daksh Khetan (he/him)
• lucasraziel - Lucas Soares Do Rego
• IamLizu - S M Mahmudul Hasan (he/him)
• Sushmeet - Sushmeet Sunger

Triagers emeriti members

Emeritus Triagers

• AuggieH - Auggie Hudak
• G-Rath - Gareth Jones
• MohammadXroid - Mohammad Ayashi
• NawafSwe - Nawaf Alsharqi
• NotMoni - Moni
• VigneshMurugan - Vignesh Murugan
• davidmashe - David Ashe
• digitaIfabric - David
• e-l-i-s-e - Elise Bonner
• fed135 - Frederic Charette
• firmanJS - Firman Abdul Hakim
• getspooky - Yasser Ameur
• ghinks - Glenn
• ghousemohamed - Ghouse Mohamed
• gireeshpunathil - Gireesh Punathil
• jake32321 - Jake Reed
• jonchurch - Jon Church
• lekanikotun - Troy Goode
• marsonya - Lekan Ikotun
• mastermatt - Matt R. Wilson
• maxakuru - Max Edell
• mlrawlings - Michael Rawlings
• rodion-arr - Rodion Abdurakhimov
• sheplu - Jean Burellier
• tarunyadav1 - Tarun yadav
• tunniclm - Mike Tunnicliffe

License

MIT