localStorage vs sessionStorage vs cookies: which one to use?The practical differences between localStorage, sessionStorage and cookies — capacity, lifetime, security and when to pick each one.What is a Regular Expression (regex)? A practical guideA regular expression (regex or regexp) is a sequence of characters that forms a search pattern for matching and manipulating text. Built on a formal mathematical foundation and common to almost every programming language and tool, regex lets you validate input, find and replace text, extract data, and transform strings with a compact, declarative syntax. This guide explains what regex is, its core syntax, how it is implemented, and how to use it safely.What is code splitting? How it works and when to use itCode splitting divides a JavaScript bundle into smaller chunks that load on demand, speeding up initial page load. This guide explains the technique, the tools, and when it matters most.What is CSRF (Cross-Site Request Forgery)? How it works and how to prevent itCross-Site Request Forgery (CSRF) tricks a logged-in browser into sending unwanted requests to a trusted site. This guide explains how the attack works and the defenses that stop it.What is Object-Oriented Programming (OOP)? A complete guideObject-oriented programming is a paradigm based on objects that combine data and behavior. Learn the four pillars — encapsulation, inheritance, polymorphism, and abstraction — with practical examples and how they work in JavaScript, Java, and Python.What is Server-Side Rendering (SSR)? How it works and when to use itServer-side rendering generates the full HTML for a page on the server in response to a request — delivering a complete, crawlable page to the browser. Here's how SSR works, how it compares to client-side rendering, and when it makes sense for your project.What is WebAssembly (WASM)? How it works and when to use itWebAssembly is a binary instruction format for a stack-based virtual machine — a portable compilation target that lets you run C, C++, Rust, and other compiled languages in the browser and beyond. Here's how it works and when it's worth using.What is XSS (Cross-Site Scripting)? How it works and how to prevent itCross-Site Scripting (XSS) lets an attacker run their own JavaScript in another user's browser. This guide explains how the three types work and the defenses that stop them.What is unit testing? How to write, structure, and run unit testsUnit testing is the practice of testing the smallest testable parts of a program — functions, methods, or classes — in isolation. Learn what a unit test is, the arrange-act-assert structure, test doubles and mocking, the testing pyramid, and best practices for writing good unit tests.What is the JavaScript event loop? How the call stack, task queue, and microtask queue workThe JavaScript event loop is the runtime model that lets single-threaded JavaScript run asynchronous code. Learn how the call stack, the task queue, and the microtask queue cooperate, and why Promise callbacks fire before setTimeout.What is JSON? The complete guide to JavaScript Object NotationJSON (JavaScript Object Notation) is an open, language-independent, text-based data interchange format derived from JavaScript object syntax. It represents data as a small set of types — objects, arrays, strings, numbers, booleans, and null — and is the de facto format for web APIs, configuration files, and data exchange between servers and clients. This guide explains JSON's syntax, its data types, how it compares to XML and YAML, and how to parse and generate it.How to build a REST API with Node.js and ExpressLearn to create a production-ready RESTful API using Node.js and Express: setup, routing, middleware, environment variables, error handling, and deployment best practices — with a practical CRUD example for managing resources.What is a Service Worker? How it works and when to use itA service worker is a JavaScript file the browser runs in the background, separate from the page. It sits between your app and the network and lets you cache assets, intercept requests, work offline, and receive push notifications. Here's how it works, what its lifecycle looks like, and when to reach for one.TypeScript vs JavaScript: which language should you learn first?JavaScript is the language of the web; TypeScript is a typed superset of it that compiles to JavaScript. Compare the trade-offs and learn when each one is the right tool. 