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express

Fast, unopinionated, minimalist web framework

    4.18.3latest
    GitHub
    npm

Version published
Maintainers
6
Weekly downloads
30,631,759
increased by5.02%

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Package description

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

Readme

Source

Express Logo

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

NPM Version NPM Install Size NPM Downloads

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

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

Linux Build Windows Build Test Coverage

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

The current lead maintainer is Douglas Christopher Wilson

List of all contributors

License

MIT

Keywords

FAQs

Last updated on 29 Feb 2024

Did you know?

Socket installs a GitHub app to automatically flag issues on every pull request and report the health of your dependencies. Find out what is inside your node modules and prevent malicious activity before you update the dependencies.

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