Node.js Cheat Sheet

A fast, scannable reference covering the syntax and patterns from across this entire Node.js course, useful while actively building rather than re-reading full lessons.

How to Use This Cheat Sheet

Each table below groups related syntax by topic, core modules, async patterns, Express, databases, and security essentials, matching the structure of this course. Use it as a quick lookup while coding, and jump back to the full lesson whenever you need the deeper explanation behind a pattern.

import fs from 'node:fs/promises';
import path from 'node:path';
import express from 'express';

const app = express();
app.use(express.json());

app.get('/health', (req, res) => res.json({ status: 'ok' }));
app.listen(process.env.PORT || 3000);

A minimal but representative snippet touching several of the topics covered in the tables below.

Running and Managing a Project

node app.js                 # run a script
node --watch app.js          # auto-restart on changes
npm install express           # add a dependency
npm run dev                    # run a package.json script
node --test                     # run tests with the built-in runner

node --watch restarts your script automatically on file changes, no extra package required.
npm run <script> executes anything defined under package.json's scripts field.
node --test runs the built-in test runner across *.test.js files.

Core Modules Quick Reference

The built-in modules covered throughout this course.

Module	Common Use	Example
`node:fs`	Read/write files	`await fs.readFile(path, 'utf8')`
`node:path`	Build cross-platform paths	`path.join(a, b, 'c.txt')`
`node:http`	Raw HTTP server	`http.createServer(handler)`
`node:crypto`	Hashing, random values	`crypto.randomUUID()`
`node:os`	System information	`os.cpus().length`
`node:events`	Custom event emitters	`class X extends EventEmitter`
`node:worker_threads`	CPU-bound parallelism	`new Worker('./worker.js')`
`node:child_process`	Run external commands	`spawn(cmd, args)`

Async Patterns Quick Reference

Pattern	Example
Callback	`fs.readFile(path, (err, data) => {})`
Promise	`fs.promises.readFile(path).then((data) => {})`
Async/await	`const data = await fs.promises.readFile(path);`
Parallel	`await Promise.all([a(), b(), c()]);`
Settle all	`await Promise.allSettled([a(), b()]);`

Express Quick Reference

Task	Code
Create app	`const app = express();`
Route	`app.get('/path', handler)`
Middleware	`app.use(middleware)`
Route param	`req.params.id`
Query string	`req.query.page`
JSON response	`res.json(data)`
Status code	`res.status(201).json(data)`
Error middleware	`app.use((err, req, res, next) => {})`

Database Quick Reference

Task	Example
PostgreSQL query	`pool.query('SELECT * FROM t WHERE id = $1', [id])`
MySQL query	`pool.query('SELECT * FROM t WHERE id = ?', [id])`
MongoDB find	`collection.find({ field: value }).toArray()`
Mongoose create	`await Model.create(data)`
Mongoose find by id	`await Model.findById(id)`

Security Quick Reference

Task	Code
Security headers	`app.use(helmet())`
CORS	`app.use(cors({ origin: allowedOrigins }))`
Rate limiting	`app.use(rateLimit({ windowMs, max }))`
Hash a password	`await bcrypt.hash(password, 12)`
Verify a password	`await bcrypt.compare(password, hash)`
Sign a JWT	`jwt.sign(payload, secret, { expiresIn: '1h' })`
Verify a JWT	`jwt.verify(token, secret)`

Common Mistakes

Using this cheat sheet as a substitute for understanding why each pattern works the way it does.
Copying a snippet without checking it matches your project's module system (CommonJS vs ESM).
Skipping the security quick reference when shipping a new API endpoint.
Not revisiting the full lesson when a quick-reference snippet doesn't behave as expected.

Key Takeaways

This cheat sheet consolidates syntax from every major topic covered in this Node.js course.
Core modules, async patterns, Express, databases, and security each have a dedicated quick-reference table.
Use it for fast lookups while coding, and the full lessons for deeper understanding.
Bookmark this page as your go-to reference while building real Node.js projects.

Pro Tip

Keep this cheat sheet open in a browser tab while working through your first few real Node.js projects. Referencing exact syntax quickly, rather than context-switching to search engines repeatedly, keeps you in flow while you're still building muscle memory for these patterns.