TypeScript Basics
📌 Covered in this chapter:
Interfaces · Type Aliases · Union Types · Generics · Type Narrowing
Learn the TypeScript fundamentals you need before adding types to a Node.js backend: interfaces, unions, and generics.
1TypeScript Basics — What You'll Learn
Learn the TypeScript fundamentals you need before adding types to a Node.js backend: interfaces, unions, and generics.
Here's everything this chapter covers, in the order you'll learn it:
- What TypeScript is and why teams adopt it
- Interfaces
- Type aliases
- Union types
- Generics
- Function types
- Type narrowing
- Enums (overview)
- Optional properties
- Typing API response shapes
2Working Example
💻 Example: TypeScript Basics
TypeScript
▶ Run in Compiler
type Course = {
id: number;
title: string;
level: string;
};
function formatCourse(course: Course): string {
return `${course.title} - ${course.level}`;
}3Best Practices & Common Pitfalls
💡 Key things to remember:
- TypeScript compiles down to plain JavaScript — Node.js itself doesn't run TypeScript directly, which is why a build (or a tool like tsx) is needed.
❓ Frequently Asked Questions (FAQ)
Q What's the most important thing to understand about typescript basics?
Focus on: Interfaces · Type Aliases · Union Types · Generics · Type Narrowing. These are the core building blocks this chapter's examples are built around, and they show up repeatedly in later chapters of this course.
Q Do I need external npm packages for typescript basics?
Only where explicitly shown in the code examples above (like Express, Zod, or Socket.IO) — otherwise, this chapter relies entirely on Node.js's own built-in capabilities.