Easy everything in Node.js & Express, page 2
Parse JSON and URL-encoded bodies in Express
Express.json() for JSON, express.urlencoded() for form data, both registered via app.use().
What is Express middleware
Middleware are functions in a chain with req, res, next, they inspect or modify request and response, then call next to continue or send a response to end.
Query params vs route params in Express
Query string values via req.query.q, named path segments via req.params.id, query is optional, route params are part of the matched pattern.
Serving static files in Express
App.use with express.static pointing at the public directory, files served relative to that root, often combined with an absolute path.
Minimal Express Hello World server
Import express, create an app, define app.get on the root sending a response, call app.listen on a port.
Minimal HTTP server with the http module
CreateServer with a request listener, set status and Content-Type, end the response, call listen on 3000.
Why use path.join over string concatenation
Path.join uses the correct OS separator, collapses duplicate slashes, normalizes . and .. segments.
fs.readFileSync vs fs.readFile
Sync blocks the event loop and returns directly, async takes a callback or promise, only sync is safe at startup.
The three states of a JavaScript Promise
Pending, fulfilled, rejected; settle is one-way and final; create with the executor calling resolve or reject, consume with then and catch.
Resolving core vs relative module specifiers
'fs' is a built-in core module loaded by name with top priority; './my-file.js' is a relative path resolved from the current file.
dependencies vs devDependencies in package.json
Dependencies ship and run in production; devDependencies are only for development; omitted with npm install --production.
The WebSocket Protocol
WebSocket (RFC 6455) is a protocol providing full-duplex, persistent communication over a single TCP connection. It begins as an HTTP request that upgrades, then both client and server can send messages anytime, enabling real-time apps without HTTP's…
How does Node.js handle thousands of connections on one thread?
This tests non-blocking I/O: Node.js runs one thread for an event loop while the OS handles sockets via epoll or IOCP, resuming callbacks when data arrives. Mention the thread pool for DNS and fs work. A red flag is claiming threads spawn per request.
Node.js Built-in SQLite Driver
Node.js bundles a SQLite driver in node:sqlite. Open a file with new DatabaseSync(path), then run SQL with exec() or prepared statements. Use it for local tools and caches. DatabaseSync is synchronous, so running it on a web server main thread blocks requests.
ODM: Your Database as JavaScript Objects
ODM translates JavaScript objects to database records and back, letting you work with plain objects instead of raw queries. It removes boilerplate in Node.js apps but hides the real queries underneath.
Node.js Callbacks: Functions That Run Later
A callback is a function you pass to run later when an event fires or work finishes, keeping Node.js free to handle other work. HTTP servers use them to respond to connections without blocking.
Creating a Basic Node.js Dockerfile
A Dockerfile is a recipe for building a portable image of your app. Use it to ensure your Node.js app runs identically everywhere, from your laptop to production.
PM2: The Process Manager for Production Node.js
PM2 is a process manager that keeps your Node.js apps online. Use it to automatically restart crashed apps, run them in the background, and scale across CPU cores. The footgun is forgetting to run pm2 save to make your process list survive server reboots.
NODE_ENV: Flipping the 'Production' Switch
Setting NODE_ENV=production is like telling your Node.js app it's showtime, not rehearsal. This triggers performance optimizations in frameworks like Express, such as view caching and less verbose errors.
Socket.IO: Emitting and Handling Events
Socket.IO events are named messages sent between a client and server. One side emits a message, the other listens with on. This powers real-time apps like chat. The footgun: don't JSON.stringify objects; Socket.IO does it for you.
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