TypeScript Lesson 2: Setup & tsconfig.json

Let’s install TypeScript and configure a project properly. tsconfig.json is the brain of every TypeScript project.

Installation

# Install TypeScript globally
npm install -g typescript

# Verify:
tsc --version  # 5.x.x

# OR use in a project (recommended):
mkdir my-ts-project && cd my-ts-project
npm init -y
npm install -D typescript
npx tsc --init  # creates tsconfig.json

tsconfig.json Explained

{
  "compilerOptions": {
    "target": "ES2022",      // output JS version
    "module": "commonjs",    // module system
    "outDir": "./dist",      // compiled JS goes here
    "rootDir": "./src",      // TypeScript source here
    "strict": true,          // ALWAYS enable this!
    "esModuleInterop": true,
    "skipLibCheck": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "dist"]
}

Your First TypeScript File

// src/hello.ts
const message: string = "Hello, TypeScript!";
const count: number = 42;
const active: boolean = true;

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

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

// Compile and run:
npx tsc          // compiles src/ → dist/
node dist/hello.js  // run the compiled JS

// Or use ts-node to run directly:
npm install -D ts-node
npx ts-node src/hello.ts