const a = Array.from({ length: 3 }, (_, i) => i + 1); // [1, 2, 3]
const last = a.at(-1); // 3

const nums = [3, 1, 4, 1, 5];

const sorted = nums.toSorted((x, y) => x - y);
const replaced = nums.with(2, 99); // [3, 1, 99, 1, 5]
const unique = [...new Set(nums)];

function chunk(arr, size) {
  const out = [];
  for (let i = 0; i < arr.length; i += size) {
    out.push(arr.slice(i, i + size));
  }
  return out;
}

const people = [
  { name: "Ada", role: "eng" },
  { name: "Alan", role: "eng" },
  { name: "Grace", role: "ops" },
];
const byRole = Object.groupBy(people, (p) => p.role);

const nested = [[1, 2], [3], [4, 5]];
console.log(nested.flat()); // [1, 2, 3, 4, 5]

const freq = nums.reduce((m, n) => {
  m.set(n, (m.get(n) ?? 0) + 1);
  return m;
}, new Map());

const [head, ...tail] = nums;
const copy = [...nums, 9];

const sparse = [];
sparse[2] = "x";
console.log(sparse.length); // 3

const chars = Array.from("hi"); // ["h", "i"]

// Stable partition
const evens = nums.filter((n) => n % 2 === 0);
const odds = nums.filter((n) => n % 2 !== 0);