🔃 Functions & Scope

Defining Functions

Function declaration (hoisted — usable before it's defined):

function add(a, b) { return a + b; }

Arrow function (modern, concise — preferred in most modern code):

const add = (a, b) => a + b;
const square = n => n * n; // single param: no parens needed

Default parameters: function greet(name, formal = false) — if formal is not provided, it defaults to false.

Scope

Block scope: const and let declared inside { } are only accessible within those braces. Variables declared outside any function are global.

Closure: An inner function can access variables from its outer function even after the outer function has returned. This is one of JavaScript's most powerful (and occasionally confusing) features.