TypeScript Fundamentals

Practical TypeScript reference covering the type system, advanced patterns, and real-world usage across different project contexts. Organized as runnable examples with inline commentary on non-obvious behavior.

Topics

Area	Coverage
Core Types	Primitives, arrays, tuples, enums, union/intersection types
Type Narrowing	typeof, instanceof, discriminated unions, assertion functions
Generics	Generic functions, classes, constraints, conditional types
Utility Types	Partial, Required, Pick, Omit, Record, ReturnType, and more
Template Literals	Mapped types, template literal types, infer keyword
Modules	ES modules, declaration files, path aliases
Config	tsconfig.json options, strict mode, project references
Patterns	Builder pattern, factory functions, branded types, type guards

Structure

src/
├── basics/           # Core type system and primitives
├── generics/         # Generic patterns and constraints
├── utility-types/    # Built-in utility type examples
├── advanced/         # Conditional types, infer, mapped types
└── patterns/         # Real-world design patterns in TypeScript

Running Examples

npm install
npx ts-node src/<topic>/index.ts

Or compile and run:

npx tsc
node dist/<topic>/index.js

Prerequisites

• Node.js 18+
• TypeScript 5+