Use modern array and object methods

const users = [
  { id: 1, name: 'Alice', age: 32, active: true },
  { id: 2, name: 'Bob', age: 17, active: false },
  { id: 3, name: 'Carol', age: 25, active: true }
]
 
// map() — transform every element
const names = users.map(u => u.name)
// ['Alice', 'Bob', 'Carol']
 
// filter() — select matching elements
const adults = users.filter(u => u.age >= 18)
// [Alice, Carol]
 
// find() — first matching element
const alice = users.find(u => u.name === 'Alice')
 
// findIndex() — index of first match
const bobIndex = users.findIndex(u => u.id === 2)
 
// some() / every() — boolean checks
const hasMinors = users.some(u => u.age < 18)    // true
const allActive = users.every(u => u.active)      // false

// Sum a property
const totalAge = users.reduce((sum, u) => sum + u.age, 0)
 
// Group by a property
const byActive = users.reduce((groups, user) => {
  const key = user.active ? 'active' : 'inactive'
  return { ...groups, [key]: [...(groups[key] ?? []), user] }
}, {})

const orders = [
  { id: 1, items: ['shirt', 'pants'] },
  { id: 2, items: ['shoes'] },
  { id: 3, items: ['jacket', 'scarf', 'gloves'] }
]
 
// Get all items across all orders (flat)
const allItems = orders.flatMap(order => order.items)
// ['shirt', 'pants', 'shoes', 'jacket', 'scarf', 'gloves']

const prices = { apple: 1.20, banana: 0.50, cherry: 3.00 }
 
// Object.entries() — iterate as [key, value] pairs
Object.entries(prices).forEach(([fruit, price]) => {
  console.log(`${fruit}: $${price}`)
})
 
// Transform an object (entries → map → fromEntries)
const discounted = Object.fromEntries(
  Object.entries(prices).map(([k, v]) => [k, v * 0.9])
)
 
// Object.keys() and Object.values()
const fruits = Object.keys(prices)
const amounts = Object.values(prices)

// ❌ Shallow clone — nested objects still shared
const copy = { ...original }
 
// ❌ Brittle hack for deep clone
const deep = JSON.parse(JSON.stringify(original)) // loses Date, undefined, functions
 
// ✅ Modern deep clone
const deep = structuredClone(original) // Handles Date, Map, Set, circular refs

// Convert NodeList, Set, arguments to arrays
const elements = Array.from(document.querySelectorAll('.item'))
const unique = Array.from(new Set([1, 2, 2, 3, 3]))
const range = Array.from({ length: 5 }, (_, i) => i + 1) // [1, 2, 3, 4, 5]