TypeScript for JS Developers
TypeScript is JavaScript with a type system bolted on. Every JavaScript file is valid TypeScript — you just add type annotations where they help. This course teaches TypeScript through real-world patterns: typed functions, interfaces, generics, and the exact configuration setup used in Next.js and React projects.
What you'll learn
Course outline
Free — no account needed
What Is TypeScript?
JavaScript with a spell-checker that knows what type every variable is
Basic Types
string, number, boolean, array, and the special cases that trip people up
Interfaces and Type Aliases
How to describe the shape of objects — the most important TypeScript skill
Full course — $59 one-time
Functions and Generics
Typed functions, optional parameters, overloads, and writing reusable code with generics
Type Narrowing and Guards
How TypeScript figures out which type you have inside an if-block
TypeScript with React
Typed props, event handlers, useState, useRef, and component patterns
Utility Types
Partial, Required, Pick, Omit, Record — the built-in tools that save you from repeating type definitions
tsconfig.json Explained
The config file that controls how strict TypeScript is — and what the important options mean
TypeScript with APIs
Typing fetch responses, Zod for runtime validation, and keeping client and server in sync
Migrating a JS Project to TypeScript
A practical step-by-step playbook for adding TypeScript to an existing JavaScript codebase
Get the full course
10 lessons — from JavaScript types to full TypeScript + React + Zod production patterns.