JavaScript 2025 cheatsheet

JavaScript 2025: Objects and data

9 common JavaScript 2025 tasks.

Destructure an object

Pull properties into variables, with a default for a missing one.

const { name, email = "none" } = user;

Use array destructuring to swap without a temporary variable.

[a, b] = [b, a];

Combine objects. Later properties win.

const settings = { ...defaults, ...overrides };

Iterate over keys and values.

for (const [key, value] of Object.entries(obj)) {
  console.log(key, value);
}

Turn an array of [key, value] pairs into an object.

const obj = Object.fromEntries([["a", 1], ["b", 2]]);

Return undefined instead of throwing when something in the chain is null or undefined.

const city = user?.address?.city;

Unlike ||, it keeps 0 and empty strings.

const port = config.port ?? 3000;

Copy nested data, including dates and maps.

const copy = structuredClone(original);

Pretty-print an object as JSON, and parse JSON text back.

const text = JSON.stringify(data, null, 2);
const parsed = JSON.parse(text);