TypeScript Essentials

Introduction to TypeScript

Beginner Lesson 1 of 9

Introduction to TypeScript

TypeScript is a typed superset of JavaScript that compiles to plain JavaScript.

Why TypeScript?

Type Safety - Catch errors at compile time
Better IDE Support - Autocomplete, refactoring, navigation
Self-Documenting - Types serve as documentation
Scalability - Easier to maintain large codebases

Setup

# Install TypeScript
npm install -g typescript

# Initialize project
tsc --init

# Compile TypeScript
tsc file.ts

# Watch mode
tsc --watch

Basic Types

// Primitives
let name: string = "Alice";
let age: number = 25;
let isActive: boolean = true;

// Arrays
let numbers: number[] = [1, 2, 3];
let names: Array<string> = ["Alice", "Bob"];

// Tuple
let tuple: [string, number] = ["Alice", 25];

// Any (avoid when possible)
let anything: any = "could be anything";

// Unknown (safer than any)
let unknown: unknown = 4;

Type Inference

// TypeScript infers the type
let message = "Hello"; // string
let count = 42;        // number

// No need to annotate when type is obvious
const user = {
  name: "Alice",
  age: 25
}; // { name: string; age: number }

Functions

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

// Optional parameters
function greet(name: string, greeting?: string): string {
  return `${greeting || "Hello"}, ${name}!`;
}

// Default parameters
function greet(name: string, greeting: string = "Hello"): string {
  return `${greeting}, ${name}!`;
}

// Arrow functions
const add = (a: number, b: number): number => a + b;

Next Steps

Continue to TypeScript Setup →