Function Types in TypeScript

// Function declaration
function add(a: number, b: number): number {
  return a + b
}

// Arrow function
const multiply = (a: number, b: number): number => a * b

// Function type
type MathFn = (a: number, b: number) => number
const subtract: MathFn = (a, b) => a - b

// Optional parameters
function greet(name: string, title?: string): string {
  return title ? `${title} ${name}` : `Hello ${name}`
}

// Default parameters
function log(message: string, level: string = "info"): void {
  console.log(`[${level}] ${message}`)
}