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TypeScript Crash Course

TypeScript is JavaScript with superpowers. It adds static typing to JavaScript, catching errors at compile time instead of runtime. If you’re building anything serious — from React apps to Node.js APIs — TypeScript is the industry standard.
This crash course takes you from basic types to advanced patterns like generics, decorators, and type gymnastics.

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Why TypeScript?

TypeScript has become the default choice for professional JavaScript development.

Catch Errors Early

Static typing catches bugs before your code runs. No more “undefined is not a function” in production.

Better IDE Experience

Autocomplete, refactoring, and inline documentation powered by the type system.

Scales with Your Team

Types serve as documentation. Large codebases become manageable and self-documenting.

JavaScript Compatible

TypeScript is a superset of JavaScript. Any valid JS is valid TS. Migrate gradually.

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Course Roadmap

We’ll build your TypeScript knowledge from the ground up.
1

Fundamentals

Types, type inference, and basic annotations. Start Learning
2

Functions & Types

Function types, overloads, generics basics, and type guards. Master Functions
3

Objects & Interfaces

Interfaces, type aliases, optional properties, and index signatures. Define Structures
4

Classes & OOP

Classes, access modifiers, abstract classes, and decorators. Go Object-Oriented
5

Advanced Types

Union, intersection, conditional types, mapped types, and utility types. Level Up
6

Generics Deep Dive

Generic functions, classes, constraints, and real-world patterns. Master Generics
7

Modules & Configuration

ES modules, namespaces, tsconfig.json, and project setup. Configure Projects

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Prerequisites

  • Strong understanding of JavaScript (ES6+).
  • Familiarity with Node.js and npm.
  • Basic understanding of object-oriented concepts.
  • A code editor with TypeScript support (VS Code recommended).

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The TypeScript Philosophy

“TypeScript is a strict syntactical superset of JavaScript that adds optional static typing.” — Microsoft
TypeScript’s design goals:
  • Statically identify constructs that are likely to be errors.
  • Provide a structuring mechanism for larger pieces of code.
  • Impose no runtime overhead on emitted programs.
  • Align with current and future ECMAScript proposals.
// A taste of TypeScript
interface User {
  id: number;
  name: string;
  email: string;
  role: 'admin' | 'user' | 'guest';
}

function greetUser(user: User): string {
  return `Hello, ${user.name}! You are logged in as ${user.role}.`;
}

const user: User = {
  id: 1,
  name: 'Alice',
  email: '[email protected]',
  role: 'admin'
};

console.log(greetUser(user)); // "Hello, Alice! You are logged in as admin."

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Setting Up TypeScript

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Installation

# Install globally
npm install -g typescript

# Check version
tsc --version

# Initialize a project
tsc --init

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Your First TypeScript File

// hello.ts
function greet(name: string): string {
  return `Hello, ${name}!`;
}

console.log(greet('World'));

# Compile to JavaScript
tsc hello.ts

# Run the compiled JS
node hello.js

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Using ts-node (No Compile Step)

# Install ts-node
npm install -g ts-node

# Run TypeScript directly
ts-node hello.ts
Pro Tip: Use tsx for even faster execution: npm install -g tsx && tsx hello.ts

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TypeScript vs JavaScript

FeatureJavaScriptTypeScript
Type SystemDynamicStatic (optional)
Error DetectionRuntimeCompile time
IDE SupportBasicRich (autocomplete, refactoring)
Learning CurveLowerHigher (but worth it)
CompilationNot requiredRequired (to JS)
AdoptionUniversalGrowing rapidly
Let’s dive into the fundamentals and start writing type-safe code!