Glossary
Discriminated Unions
2.0 A union of types that each carry a shared literal field (the discriminant) allowing TypeScript to narrow exhaustively — the canonical way to model mutually exclusive states.
2mo ago
typescript intermediate
Module Augmentation & Declaration Merging
2.0 Module augmentation lets you extend third-party or global type definitions without modifying their source — adding properties to existing interfaces, modules, or the global scope.
2mo ago
typescript advanced
Recursive Types
3.7 Types that reference themselves to describe arbitrarily nested structures — trees, nested menus, JSON, linked lists — without requiring any escape hatch.
2mo ago
typescript advanced
Type Guards & Narrowing
2.0 Type guards are expressions that narrow a union type to a more specific type at runtime — telling TypeScript exactly which branch of a union you're in.
2mo ago
typescript intermediate
async / await in JavaScript
ES2017
5
async functions always return a Promise; await pauses execution inside an async function until a Promise settles — giving asynchronous code the readability of synchronous code without blocking the event loop.
2mo ago
javascript intermediate
Brute-Force Protection
Defences against automated credential-guessing attacks — rate limiting login attempts, account lockout, CAPTCHA, and multi-factor authentication to make guessing passwords computationally infeasible.
CWE-307 OWASP A7:2021
2mo ago
security intermediate
ES Modules (ESM)
ES2015
The official JavaScript module system — import and export statements enable static dependency graphs, tree-shaking, and native browser module loading without a bundler.
2mo ago
javascript intermediate
Fetch API
ES2015
The browser-native Promise-based API for making HTTP requests — replacing XMLHttpRequest with a cleaner interface supporting streaming, CORS, and request/response objects.
2mo ago
javascript beginner
HTTP Cookies in PHP
PHP 7.3+
Cookies are small key-value pairs sent by the server via Set-Cookie and echoed back by the browser on every request — PHP sets them with setcookie() before any output, with Secure, HttpOnly, and SameSite flags controlling safety.
2mo ago
php beginner
Insecure Deserialization
Deserializing attacker-controlled data can trigger arbitrary object construction and method calls — PHP's unserialize() with untrusted input enables remote code execution via gadget chains in the loaded class graph.
CWE-502 OWASP A8:2021
2mo ago
security advanced
Memory Management in JavaScript
JavaScript uses automatic garbage collection — the engine reclaims memory when objects are no longer reachable. Memory leaks occur when references are unintentionally retained, preventing collection.
2mo ago
javascript intermediate
OAuth 2.0
An authorisation framework that lets users grant third-party applications limited access to their resources without sharing passwords — using short-lived access tokens issued via defined flows for different client types.
CWE-287 OWASP A7:2021
2mo ago
security intermediate
Timing Attacks
Side-channel attacks that infer secret values by measuring how long an operation takes — a string comparison that short-circuits on the first mismatch leaks information about the secret one character at a time.
CWE-208
2mo ago
security advanced
Canonical URL (rel=canonical)
1
A <link rel='canonical'> tag that tells search engines which URL is the authoritative version of a page — preventing duplicate content from splitting ranking signals across multiple URLs.
2mo ago
frontend intermediate
Core Web Vitals
Google's three field-measured performance metrics — LCP (loading), INP (interactivity), CLS (visual stability) — used as direct search ranking signals since 2021.
2mo ago
performance intermediate
Cumulative Layout Shift (CLS)
A Core Web Vital that measures unexpected visual movement of page elements during load — caused by images without dimensions, late-injected content, and font swaps. Target: under 0.1.
2mo ago
performance intermediate
Dependency & Supply Chain Security
Protecting applications from malicious or vulnerable third-party packages — covering transitive dependencies, lock files, SRI hashes, CVE scanning, and supply chain attack vectors.
CWE-1357 OWASP A6:2021
2mo ago
security intermediate
HTML lang Attribute
The lang attribute on <html> declares the page's primary language — required for screen readers to select the correct voice profile and pronunciation rules, and for WCAG 2.1 compliance.
2mo ago
accessibility beginner
HTML Meta Tags
Tags in <head> that provide page metadata — title, description, viewport, Open Graph — for browsers, search engines, and social platforms.
2mo ago
frontend beginner
Image Optimisation
Reducing image file size and delivery overhead through format choice (AVIF, WebP), compression, responsive sizing (srcset), lazy loading, and explicit dimensions — the single highest-impact performance lever for most websites.
2mo ago
performance intermediate