Express Docs

Express Expert (v5.x)

Official Documentation: https://expressjs.com/ GitHub: https://github.com/expressjs/express

What is Express?

Express is a fast, unopinionated, minimalist web framework for Node.js. It provides a robust set of features for web and mobile applications, including routing, middleware, template rendering, and API development.

Quick Reference

| Topic | File | |------|------| | Getting Started (install, hello world, generator, static files, FAQ) | getting-started.md | | Routing (methods, paths, params, handlers, app.route, Router) | routing.md | | Middleware (writing, using, app-level, router-level, error, built-in, third-party) | middleware.md | | Error Handling (catching errors, handlers, async patterns) | error-handling.md | | API: express() & Application Object | api-app.md | | API: Request Object (req properties & methods) | api-request.md | | API: Response Object (res properties & methods) | api-response.md | | API: Router Object (router methods) | api-router.md | | Template Engines (using, developing, rendering) | template-engines.md | | Debugging (DEBUG env var, debugging routes, views) | debugging.md | | Database Integration (MongoDB, MySQL, PostgreSQL, Redis) | database.md | | Security (best practices, helmet, CORS, rate limiting) | security.md | | Performance (best practices, caching, clustering) | performance.md | | Production (healthcheck, graceful shutdown, behind proxies) | production.md | | Migration (to Express 4, to Express 5, breaking changes) | migration.md | | Overriding Express API (methods, properties, TypeScript) | overriding-api.md | | Security Updates (CVEs, vulnerabilities, patches) | security-updates.md |

Hello World

import express from 'express';
const app = express();
const port = 3000;

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

Project Structure

myapp/
  app.js              # Main application file
  routes/
    index.js          # Route handlers
    users.js
    api/
      v1.js
  middleware/
    auth.js
    logger.js
  public/             # Static assets
    images/
    css/
    js/
  views/              # Template files
    index.ejs
    layout.ejs
  package.json

Key Concepts

• Middleware — Functions that execute during the request-response cycle
• Routing — Maps HTTP methods and URLs to handler functions
• Application Object — The app object created by express()
• Request Object — req represents the HTTP request
• Response Object — res represents the HTTP response
• Router — Isolated instance of middleware and routes (modular routing)
• Template Engines — Server-side rendering with EJS, Pug, Handlebars, etc.
• Error Handling — Centralized error handling via error middleware
• Express 5 — Async error support, path-to-regexp v8, removed deprecated APIs

Prerequisites

• Node.js (v18+ recommended for Express 5)
• JavaScript fundamentals
• HTTP basics (methods, headers, status codes)
• npm/pnpm/yarn package management

Installation

# Create a new project
mkdir myapp && cd myapp
npm init -y
npm install express

# Using Express generator
npx express-generator myapp
cd myapp && npm install

References

• Express Docs
• Express GitHub
• Express 5.x API
• Express GitHub Wiki
• Express Community
• Awesome Express

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: pledgeandgrow
• Source: pledgeandgrow/pledge-skills
• License: MIT

Install and usage instructions live in the source repository linked above.