The Only Node js CheatSheet Table You’ll Ever Need

Node.js is a runtime environment that allows you to execute JavaScript on the server side. It is commonly used for:
–Building RESTful APIs
–Developing real-time applications (e.g., chat apps)
–Creating server-side rendered (SSR) applications
–Streaming data and handling asynchronous tasks

Node.js uses the V8 JavaScript engine and operates on a non-blocking, event-driven architecture, which allows it to handle multiple requests concurrently without waiting for I/O operations to complete.

Node.js handles asynchronous programming using:
—Callbacks: Functions passed as arguments to execute after a task.
—Promises: Represent the eventual completion (or failure) of an asynchronous operation.
—Async/Await: Cleaner syntax to handle asynchronous code.

—require is used in CommonJS modules (default in Node.js).
—import is used in ECMAScript modules (ESM) and requires "type": "module" in package.json.
—require is synchronous, while import is asynchronous.

Use a combination of:
Try-Catch blocks: For synchronous and async/await operations.
Error callbacks: For functions using callbacks.
Global error handlers: Use process.on('uncaughtException', handler) for unhandled exceptions.

process.nextTick schedules a callback to execute before the next event loop iteration.
setImmediate schedules a callback to execute after the current event loop phase.

Use the process.env object to access environment variables.
Store variables in a .env file and use the dotenv package to load them into process.env.

Clustering: Use the cluster module to run multiple instances of your app across CPU cores.
Load Balancers: Distribute traffic among server instances using tools like NGINX.
Microservices Architecture: Break your application into smaller, independent services.

Use package.json to list dependencies.
Use npm install or yarn to manage libraries.
Regularly update dependencies with npm outdated and audit vulnerabilities with npm audit.

Use Helmet to set secure HTTP headers.
Sanitize user inputs to prevent injection attacks.
Use bcrypt for password hashing.
Implement rate limiting with tools like express-rate-limit.
Regularly scan for vulnerabilities with npm audit.

Use the Node.js Debugger with node inspect app.js.
Use debugging tools like Chrome DevTools or VS Code debugger.
Add console.log() for quick debugging (although not recommended for production).

Blocking the event loop: Avoid long-running synchronous tasks.
Memory leaks: Use tools like heapdump or node-inspect to detect leaks.
Improper database queries: Optimize queries and use connection pooling.
Poor use of streams: Use Node.js streams effectively for large data handling.

npm: Node Package Manager used to install and manage packages.
npx: Executes Node.js packages directly without installing them globally.

Use middleware like Multer for parsing multipart/form-data.
Example:

const multer = require('multer');
const upload = multer({ dest: 'uploads/' });
app.post('/upload', upload.single('file'), (req, res) => res.send('File uploaded!'));

Yes, install TypeScript and its type definitions for Node.js:

npm install typescript @types/node

Create a tsconfig.json file and compile TypeScript files to JavaScript using tsc.

Express.js: Lightweight, flexible, and popular.
Koa: Minimalist framework created by the same team as Express.
NestJS: Built with TypeScript, ideal for scalable server-side apps.
Hapi: Rich plugin architecture for building robust APIs.

Use the cors package:

const cors = require('cors');
app.use(cors());

Mocha and Chai for unit testing.
Jest for an all-in-one testing solution.
Mock APIs and services with Sinon.js or nock.

Use the ws package to handle WebSocket connections:

const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });
wss.on('connection', ws => ws.send('Hello Client'));

PM2: Process manager for Node.js apps.
New Relic or AppDynamics: For performance monitoring.
Log management tools: Use Winston or Bunyan for logging.