TypeScript — Get Started

What is TypeScript

TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. It adds static type checking to JavaScript, catching errors at compile time rather than runtime.

Installation

Install TypeScript globally with npm:

npm install -g typescript

Verify the installation:

tsc --version
# Version 5.x.x

Your first TypeScript file

Create a file called hello.ts:

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

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

Compiling TypeScript

Use the tsc compiler:

# Compile a single file
tsc hello.ts

# This generates hello.js

Run the compiled JavaScript:

node hello.js
# Hello, Alice!

Watch mode

Auto-compile on file changes:

tsc --watch

Project initialization

Create a tsconfig.json for project-wide configuration:

tsc --init

This generates a configuration file with sensible defaults:

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "commonjs",
    "strict": true,
    "esModuleInterop": true,
    "outDir": "./dist",
    "rootDir": "./src"
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules"]
}

Compile the project

# Compile all files according to tsconfig.json
tsc

# Or use watch mode
tsc --watch

ts-node for quick testing

Run TypeScript directly without compiling:

npm install -g ts-node

# Run a TypeScript file directly
ts-node hello.ts

TypeScript Playground

Try TypeScript in the browser at typescriptlang.org/play — no installation required.

Project structure

my-project/
├── src/
│   ├── index.ts
│   ├── utils.ts
│   └── types.ts
├── dist/          # Compiled output
├── tsconfig.json
└── package.json

Basic types preview

// Type annotations
let name: string = "Alice";
let age: number = 30;
let isActive: boolean = true;
let items: string[] = ["a", "b", "c"];

// Type inference
let count = 10; // TypeScript infers: number

function add(a: number, b: number): number {
    return a + b;
}

console.log(add(3, 4)); // 7

Next steps

1. Set up a project with tsc --init
2. Learn about Types — TypeScript's type system
3. Build something small to practice

Mini Practice

1. Install TypeScript and create your first .ts file
2. Compile it with tsc and run the output with node
3. Try ts-node for quick execution
4. Explore the TypeScript Playground online

Up Next

In the next lesson, you'll learn about Syntax — TypeScript's syntax rules and conventions.