Introduction to TypeScript

TypeScript brings static typing to JavaScript, making your code more maintainable and catching errors before runtime. Let's explore the basics of this powerful language.

Basic Types

TypeScript provides several basic types for variable declarations:

// Basic type annotations
let name: string = "John";
let age: number = 30;
let isActive: boolean = true;
let numbers: number[] = [1, 2, 3];
let tuple: [string, number] = ["hello", 42];

// Union types
let id: string | number = "abc123";
id = 123; // Also valid

Interfaces and Types

Define custom types for objects and function signatures:

interface User {
  id: number;
  name: string;
  email?: string; // Optional property
  readonly createdAt: Date; // Read-only property
}

type ActionHandler = (event: MouseEvent) => void;

// Using the interface
const user: User = {
  id: 1,
  name: "Alice",
  createdAt: new Date(),
};

Generics

Create reusable components that work with multiple types:

function getFirst<T>(array: T[]): T | undefined {
  return array[0];
}

// Usage
const firstNumber = getFirst([1, 2, 3]); // Type: number
const firstString = getFirst(["a", "b", "c"]); // Type: string