Destructuring Arrays & Objects

Array destructuring

Positions matter — you can skip items with an empty slot, and even swap variables in one line.

const [first, second, , fourth] = [10, 20, 30, 40];
console.log(first, second, fourth);  // 10 20 40

let [a, b] = [1, 2];
[a, b] = [b, a];   // swap
console.log(a, b); // 2 1

Object destructuring

Names matter here, not order — and you can set a default for missing keys.

const { name, age } = { name: "Ada", age: 36 };
console.log(name, age);

const { city = "Unknown" } = {};
console.log(city);  // Unknown

Renaming while destructuring

const { name: fullName } = user; pulls name out into a variable called fullName.

Quick check: What does `const [a, , b] = [1, 2, 3]` set b to?

• 2
• 3
• undefined