Destructuring arrays

// The Old Way
var temp = a, a = b, b = tmep;
[b, a] = [a, b];

var nums = [1, 2, [30, 40, [500, 600]]];
var [one,,[thirty,,[,sixhundert]]] = nums;

let ?[x, y, z] = [1, 2]  // x = 1, y = 2, z = undefined
// Only 'z' is Refutable
let [x, y, ?z] = [1, 2]  // z = 1, y = 2, z = undefined