Introduction & Setup

Introduction to TypeScript

TypeScript is a superset of JavaScript developed by Microsoft. It adds optional static typing and other features on top of JavaScript, making it easier to build and maintain large-scale applications.

Why TypeScript?

• Static type checking — catch bugs at compile time, not runtime
• Better IDE support — auto-completion, refactoring, inline docs
• Easier to maintain — types serve as documentation
• Modern JS features — use future JavaScript today

TypeScript vs JavaScript

Feature	JavaScript	TypeScript
Typing	Dynamic	Static (optional)
Compilation	Interpreted	Compiled to JS
Error detection	Runtime	Compile time
IDE support	Basic	Excellent

Setting Up

Install TypeScript globally:

npm install -g typescript
tsc -v   # Check version

Create your first TypeScript file — sandbox.ts:

let character = "Mario";
let age = 30;
let isBlackBelt = false;

console.log(character, age, isBlackBelt);

TypeScript infers types from the values you assign. Once a variable has a type, you can't reassign it to a different type:

character = "Luigi";   // ✅ OK — still a string
character = 20;        // ❌ Error — Type 'number' is not assignable to type 'string'

Key Takeaways

• TypeScript = JavaScript + static types
• It compiles down to plain JavaScript
• Types are inferred automatically from assigned values
• Install with npm install -g typescript