JavaScript Promises underpin all modern async code — and most developers use only 10% of the API. This guide covers everything from creating promises to advanced patterns with real production examples.

Closures are the most important JavaScript concept that developers understand superficially. This guide goes deep — lexical scope, closure mechanics, private state, module pattern, and common pitfalls.

TypeScript generics unlock reusable, type-safe code without any. This guide covers generic functions, constraints, conditional types, mapped types, and the infer keyword with real examples.

Functional programming in JavaScript is not about avoiding classes — it is about writing predictable, testable code with pure functions, immutability, and composition. This guide covers the practical patterns.

JavaScript manages memory automatically, but leaks still happen. This guide explains how V8 garbage collection works, how to take heap snapshots, detect leaks with Chrome DevTools, and write leak-proof code.

The Gang of Four design patterns translated to modern JavaScript — Singleton, Factory, Observer, Strategy, Command, and Proxy with ES6+ class syntax, real use cases, and when NOT to use each.

WebSockets, Server-Sent Events, and Long Polling all deliver real-time data but with different trade-offs. This guide shows when each is the right tool — chat, live dashboards, notifications, and collaborative apps.

Migrating a JavaScript project to TypeScript does not have to break everything. This guide covers the gradual adoption strategy, the tsconfig that works, and the patterns that prevent regression.

The 50 JavaScript interview questions that actually appear in senior engineer rounds at FAANG and top startups — with detailed answers covering the why, not just the what.

React hooks are deceptively simple on the surface. useState batching, useEffect dependency arrays, stale closures, useCallback stable references — these are the subtleties that cause real production bugs.