📊 Arrays & Loops

Array Methods

• .map(fn) — transforms each element, returns new array of same length
• .filter(fn) — returns new array of elements where fn returns true
• .reduce(fn, init) — reduces array to a single value (sum, object, etc.)
• .find(fn) — returns first element where fn returns true (or undefined)
• .some(fn) — returns true if any element passes; .every(fn) — all pass
• .sort(fn) — sorts in place; use compare function for numbers
• .forEach(fn) — runs fn for each element; no return value (use for side effects)

Destructuring and Spread

// Array destructuring
const [first, second, ...rest] = [1,2,3,4,5];

// Object destructuring
const { name, score } = { name: "Alex", score: 92 };

// Spread — copy/merge
const newArr = [...oldArr, 6, 7];
const merged = { ...obj1, ...obj2 };