Destructuring and spread

Pull values out of objects and arrays, then copy and merge them without mutation.

Beginner 12 min read Lesson 8 of 480 Challenge included

What you will be able to do

Destructure objects and arrays
Use rest and spread
Read nested values safely

Destructuring names the values you care about. Spread copies the rest into a new object or array, which keeps updates predictable.

modern.jsJavaScript

const learner = { name: "Ada", scores: [88, 92], cohort: "A" };

const { name, scores, cohort: group = "none" } = learner;
const [first, ...rest] = scores;
console.log(name, group, first, rest);

const updated = { ...learner, cohort: "B" };
const merged = [...scores, 79];
console.log(updated.cohort, merged);

const email = learner?.contact?.email ?? "not provided";
console.log(email);

const settings = { theme: null };
console.log(settings.theme ?? "light");

Syntax	Meaning
const { a, b } = obj	Read named properties
const [first, ...rest] = list	Take the first item and the rest
{ ...obj, key: value }	Copy then override
obj?.a?.b	Stop safely when a value is nullish
value ?? fallback	Fallback only for null or undefined

Your turn

Build a learner summary

Easy

Create a new object with fullName and best score, without changing the input objects.

JAVASCRIPT · starter

const user = { first: "Ada", last: "Lovelace" };
const scores = [88, 92, 79];
// your code here

Check your understanding before moving on.

Knowledge checkQuestion 1

What is the value of a in const { a = 5 } = {}?

Select an answer to continue

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