JavaScript & TypeScript

Values & Types — What JavaScript Actually Has

Equality & Coercion — == vs === and Why It Matters

Scope & Hoisting — let, const, var and the TDZ

Closures — Functions That Remember

`this` — Four Rules and an Arrow Function

Prototypes — How Inheritance Actually Works

Functions — Declarations, Expressions, Arrows, Defaults

Modules — import, export and the CommonJS Split

Arrays — map, filter, reduce and the Rest

Objects — Keys, Spread and Immutable Updates

Destructuring & Spread — Pulling Data Apart

Strings — Templates, Methods and Unicode

Map & Set — When a Plain Object Is Not Enough

JSON — Serialising, Parsing and the Sharp Edges

The Event Loop — One Thread, No Blocking

Promises — States, Chaining and the Combinators

async / await — Promises That Read Like Sequential Code

fetch — Talking to Your API

Errors — Throwing, Catching and Custom Types

Timers, Debounce and Throttle

Async Patterns — Concurrency, Queues and Cancellation

Streaming and Real-Time — SSE, WebSockets and ReadableStream

The DOM — Selecting and Changing the Page

Events — Bubbling, Delegation and Cleanup

Forms — Inputs, Validation and Submission

Browser Storage — localStorage, Cookies and IndexedDB

History & URLs — Client-Side Routing Underneath

Observers — Intersection, Resize and Mutation

Useful Browser APIs

How the Browser Renders — and Why Your Page Janks

Why TypeScript, and How It Runs

Basic Types, Inference and Annotations

Interfaces, Type Aliases and Structural Typing

Unions, Narrowing and Discriminated Unions

Generics

Utility Types

Advanced Types — Mapped, Conditional and Template Literal

Classes and OOP in TypeScript

TypeScript with React

Typing the API Boundary

Migrating and Living With TypeScript

TypeScript on the Server

npm, package.json and Dependencies

Bundlers — What They Actually Do

Build Configuration — Targets, Polyfills and Env Vars

DevTools — Debugging Beyond console.log

Workspaces, Monorepos and Shipping a Package

Testing Fundamentals — Vitest and Jest

Testing React Components

End-to-End Testing with Playwright

Linting, Formatting and CI Gates

Accessibility and Frontend Security