nodejs-express-skill

Files (5)

• SKILL.md
• app-structure.md · references/
• express-error-handling.md · references/
• express-security.md · references/
• middleware-patterns.md · references/

SKILL.md (first lines)

# Node.js Express

## Purpose
Structure Express.js applications with clean middleware pipeline, error handling, route separation, and validation.

## Agent Protocol

### Trigger
User request includes: `express`, `express.js`, `middleware`, `router`, `next.js error handling`, `express app`, `express setup`, `express routing`, `express validation`.

### Input Context
- App scope (REST API, GraphQL BFF, SSR)
- TypeScript or JavaScript
- Database (Prisma, Mongoose, raw)
- Auth strategy (JWT, session, OAuth)

### Output Artifact
Project structure, middleware order, route layout, error handler, validation setup.

### Response Format
Produce artifact directly. No preamble, no postamble, no explanations. No filler, no hedging, no transitions. Strip articles a/an/the where unambiguous. Compress output — why use many token when few do trick.

### Completion Criteria
- Middleware pipeline ordered security -> parsing -> logging -> rate-limit -> routes -> 404 -> error
- Global error handler catches sync + async errors
- All input validated via schema library
- Routes organized by domain module

### Max Response Length
4096 tokens

## Architecture Decision Trees

### Express vs Fastify vs Hono (within Node.js)

| Criterion | Express | Fastify | Hono |
|-----------|---------|---------|------|
| Performance | ~30k req/s | ~50k req/s | ~60k req/s |
| Plugin ecosystem | Largest | Growing | Small |
| TypeScript | Manual annotations | Schema-first (TypeBox/Zod) | Full (TypeBox) |
| Serialization | JSON.stringify | Fast JSON serialization | Built-in |
| Middleware model | Callback chain | Plugin registration | Express-like |
| Validation | Manual middleware | Schema-compiled serializer | Middleware-based |

Decision: Largest ecosystem / wide support → Express. Performance + schema-first → Fastify. Edge/Cloudflare Workers → Hono.

### Middleware Order Decision

| Layer | Middleware | Position |
|-------|-----------|----------|
| Security | Helmet, CORS, CSP | 1st (before any body) |
| Parsing | JSON, URL-encoded | 2nd |
| Observability | Logger, request ID | 3rd |
| Protection | Rate limiter | 4th |
| Auth | JWT/Session check | 5th |
| Routes | Domain routers | 6th |
| Fallback | 404 handler | 7th |
| Error | Global error handler | Last |

## Workflow

### Step 1: Project Bootstrap
```
express-app/
  src/
    app.ts                    # Express app factory
    server.ts                 # HTTP server entry
    config/
      env.ts                  # Typed env vars
      database.ts
      redis.ts
    modules/
      users/
        user.controller.ts
        user.service.ts
        user.repository.ts
        user.validation.ts
        user.routes.ts
        user.test.ts
      orders/
        ...
    common/
      middleware/
        auth.ts
        error-handler.ts
        request-logger.ts
        rate-limiter.ts
        validate.ts
      errors/
        app-error.ts
        not-found.ts
      types/
        express.d.ts
        index.ts
    shared/
      logger.ts
      pagination.ts
  package.json
  tsconfig.json
  .env.example
```

### Step 2: App Factory Pattern
```typescript
// app.ts
import express from 'express';
import cors from 'cors';
import helmet from 'helmet';
import compression from 'compression';
import { requestLogger } from './common/middleware/request-logger';
import { rateLimiter } from './common/middleware/rate-limiter';
import { notFoundHandler } from './common/middleware/not-found';
import { errorHandler } from './common/middleware/error-handler';
import { routes } from './modules/routes';

export function createApp() {
  const app = express();

  // Security

From j4flmao/agent-skills, MIT.

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