Node Skill
Node.js 20 LTS runtime powering Express + TypeScript backend. Uses ES modules ("type": "module") with tsx for development. PostgreSQL via pg with connection pooling. Sharp for image processing.
Quick Start
Module System (ESM)
typescript
// backend/src/server.ts - Entry point
import app from './app.js'; // .js extension required for ESM
import { env } from './config/env.js';
app.listen(env.port, () => {
console.log(`Backend listening on port ${env.port}`);
});
Environment Configuration
typescript
// backend/src/config/env.ts - Validated env with defaults
import dotenv from 'dotenv';
dotenv.config();
const required = (value: string | undefined, fallback?: string) => {
if (value) return value;
if (fallback !== undefined) return fallback;
throw new Error('Missing required environment variable');
};
export const env = {
port: Number(process.env.PORT ?? 4000),
dbHost: process.env.DB_HOST ?? 'localhost',
jwtSecret: required(process.env.JWT_SECRET, 'dev-only-secret'),
nodeEnv: process.env.NODE_ENV ?? 'development',
};
Database Connection Pool
typescript
// backend/src/db/client.ts
import pg from 'pg';
const { Pool } = pg;
export const pool = new Pool({
host: env.dbHost,
max: 20, // Max connections
idleTimeoutMillis: 30000, // Close idle after 30s
connectionTimeoutMillis: 2000,
});
pool.on('error', (err) => {
console.error('Unexpected error on idle client', err);
process.exit(-1); // Crash on pool errors
});
Key Concepts
| Concept | Usage | Example |
|---|---|---|
| ESM imports | Always use .js extension | import { x } from './mod.js' |
__dirname | Use import.meta.url | path.dirname(fileURLToPath(import.meta.url)) |
| Async/await | All I/O operations | await pool.query(...) |
| Buffer | Binary data handling | Buffer.from(data, 'hex') |
| crypto | Encryption/hashing | crypto.randomBytes(32) |
Common Patterns
Async Service Method
typescript
export const productService = {
async get(id: number, language: string = 'en') {
const result = await pool.query(
'SELECT * FROM products WHERE id = $1', [id]
);
if (!result.rows[0]) return null;
return mapProduct(result.rows[0]);
}
};
Transaction with Rollback
typescript
const client = await pool.connect();
try {
await client.query('BEGIN');
await client.query('INSERT ...', [...]);
await client.query('UPDATE ...', [...]);
await client.query('COMMIT');
} catch (error) {
await client.query('ROLLBACK');
throw error;
} finally {
client.release(); // Always release!
}
See Also
- •patterns - Async patterns, error handling
- •types - TypeScript integration
- •modules - Project structure, imports
- •errors - Error handling patterns
Related Skills
For Express routes and middleware, see the express skill. For database queries, see the postgresql skill. For TypeScript patterns, see the typescript skill.