claude-code-sample-3

Skill: Express.js JWT API with PostgreSQL and Docker

Builds a production-style Express.js REST API with JWT authentication, a PostgreSQL database, layered middleware, and Docker Compose for local development.

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When to use

When the user asks to scaffold a secure Node.js/Express REST API with login/registration, protected routes, a relational database, and containerized local development.

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Prerequisites

Make sure Node.js 18+ and npm are installed, plus Docker and Docker Compose for the database.

Set these environment variables (the app reads them at boot):

• $JWT_SECRET — secret used to sign access tokens
• $DATABASE_URL — PostgreSQL connection string
• $PORT — port the API listens on (default 3000)

Steps

Initialize the project and install dependencies:

npm init -y
npm install express jsonwebtoken bcrypt pg dotenv
npm install --save-dev nodemon

Create the file src/db.js for the PostgreSQL connection pool:

const { Pool } = require('pg');

const pool = new Pool({ connectionString: process.env.DATABASE_URL });

module.exports = { pool };

Create src/middleware/auth.js, a middleware that verifies the JWT in the Authorization: Bearer header:

const jwt = require('jsonwebtoken');

function authRequired(req, res, next) {
  const header = req.headers.authorization || '';
  const token = header.startsWith('Bearer ') ? header.slice(7) : null;
  if (!token) return res.status(401).json({ error: 'missing token' });
  try {
    req.user = jwt.verify(token, process.env.JWT_SECRET);
    next();
  } catch {
    return res.status(401).json({ error: 'invalid token' });
  }
}

module.exports = { authRequired };

Create src/middleware/logger.js, a simple request logger:

module.exports = function logger(req, res, next) {
  console.log(`${new Date().toISOString()} ${req.method} ${req.path}`);
  next();
};

Create src/routes/auth.js with POST /auth/register and POST /auth/login. Register hashes the password with bcrypt and inserts the user; login verifies the password and returns a signed JWT.