JavaScript Arrays and Objects Cheat Sheet

const nums = [1, 2, 3];

const chars = Array.from("hello");

const range = Array.from({ length: 5 }, (_, i) => i + 1);

const board = Array(9).fill(null);

const values = Array.of(5);

const names = users.map((u) => u.name);

const active = users.filter((u) => u.isActive);

const total = cart.reduce((sum, item) => sum + item.price, 0);

const flattened = nested.flat(2);

const tags = posts.flatMap((p) => p.tags);

nums.sort((a, b) => a - b);

users.sort((a, b) => a.name.localeCompare(b.name));

const newestFirst = items.toReversed();

const sorted = nums.toSorted((a, b) => a - b);

const next = items.toSpliced(1, 2, "x", "y");

const grouped = orders.reduce((acc, order) => {
  (acc[order.status] ??= []).push(order);
  return acc;
}, {});

const unique = [...new Set(values)];

const user = users.find((u) => u.id === targetId);

const idx = users.findIndex((u) => u.email === email);

const hasDraft = posts.some((p) => p.status === "draft");

const allValid = rows.every((row) => row.id != null);

const hasRole = roles.includes("admin");

const idx = tags.indexOf("urgent");

items.push(newItem);

const last = items.pop();

const first = queue.shift();

queue.unshift(priorityItem);

items.splice(1, 2, "replacement");

const copy = items.slice(0, 3);

const all = a.concat(b, c);

arr.copyWithin(1, 3, 5);

const target = Object.assign({}, sourceA, sourceB);

const own = Object.hasOwn(config, "port");

const settings = Object.freeze({ theme: "dark" });

const draft = Object.seal({ title: "" });

const snapshot = structuredClone(state);

const same = JSON.stringify(a) === JSON.stringify(b);

# Works only when property order and JSON-safe values are acceptable.

const normalized = input.trim();

const slug = title.split(" ").join("-");

const sanitized = text.replaceAll("_", "-");

file.startsWith("app-");
file.endsWith(".js");

const code = String(id).padStart(6, "0");

names.sort((a, b) => a.localeCompare(b));

for (const ch of "👍🏽JS") {
  console.log(ch);
}