Nested Arrays and Objects

Chains dot notation and bracket notation to access a value nested inside an object.

Part of: JavaScript Coding without HTML and CSS — Module 35, ACARA Digital Technologies Years 9–10 — Modular and Object-Oriented Programming (JavaScript) — Module 51

Understanding Nested Arrays and Objects in JavaScript

What it does: The first bracket picks a row, the second picks a column. The bracket picks the object, then the dot reads its property. This chains dot notation and bracket notation to reach the nested value. You can mix .property and [index] to reach deeply nested values. Two bracket accesses in a row reach into an array of arrays. Array indexes need brackets: users[0].name, not a dot. Each dot goes one level deeper into the nested object. Without quotes, city is read as a variable, not a property name.

Common mistakes: Missing the dot before pets - it should be obj.pets[0]. Missing the dot before addr - it should be obj.addr.

Class: _____________________ · Name: _____________________ · Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add Nested Arrays and Objects to a class →

This module's key terms are also in a printable crossword (Modules 31–40) and word search (Modules 21–52).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

Does person.pets[0] access an element nested inside an object?

YesNo

Matches

users.0.name

↓

Wrong - array indexes use brackets, not dots

Applying

Meanings

Term

obj.pets[0]

Meaning

Chains dot notation and bracket notation to access a value nested inside an object.

Practice

let person = {name: "Sam", pets: ["Rex", "Mia"]};

Testing

Gaps

console.log(person.pets0]);

Check Answer

Spots

1console.log(objpets[0]);

2let obj = {};

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy

Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games

Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print

Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. Does person.pets[0] access an element nested inside an object?

A. No

B. Yes ✓

This chains dot notation and bracket notation to reach the nested value.

2. Can dot notation and bracket notation be chained together?

A. Yes ✓

B. No

You can mix .property and [index] to reach deeply nested values.

3. Does grid[0][1] access an element in a 2D array?

A. No

B. Yes ✓

Two bracket accesses in a row reach into an array of arrays.

4. Is users.0.name valid syntax for accessing an array element?

A. No ✓

B. Yes

Array indexes need brackets: users[0].name, not a dot.

5. Does obj.addr.city access a property nested two levels deep?

A. Yes ✓

B. No

Each dot goes one level deeper into the nested object.

Match the Pairs

obj.pets[0] → Accesses the first element of the pets array inside obj

obj.addr.city → Accesses the city property nested inside addr inside obj

Accesses an element in a 2D array using two indexes → grid[0][1]

Accesses a property on an object stored inside an array → users[0].name

users.0.name → Wrong - array indexes use brackets, not dots

obj.addr[city] → Wrong - a nested property needs a dot, not unquoted brackets

Key Term

obj.pets[0]

Chains dot notation and bracket notation to access a value nested inside an object.

Fill in the Blanks

1. console.log(person.pets[0]);

Hint: Type the symbol that opens an index access on the nested array.

2. console.log(obj.addr.city);

Hint: Type the symbol that connects addr to its nested property.

3. console.log(users[0].name);

Hint: Type the symbol that connects the array element to its property.

4. console.log(data.scores[2]);

Hint: Type the index of the third element in scores.

5. console.log(grid[0][1]);

Hint: Type the symbol that opens the second index access.

Spot the Error

Question 1

A console.log(objpets[0]);

B let obj = {};

C obj.pets = ["Rex", "Mia"];

Line A — Missing the dot before pets - it should be obj.pets[0].

Question 2

A objaddr = {city: "NYC"};

B let obj = {};

C console.log(obj.addr.city);

Line A — Missing the dot before addr - it should be obj.addr.

Question 3

A let obj = {};

B obj.pets = ("Rex", "Mia");

C console.log(obj.pets[0]);

Line B — Arrays use square brackets [], not round brackets ().

Question 4

A let obj = {};

B obj.addr = {city: "NYC"];

C console.log(obj.addr.city);

Line B — Object literals close with }, not ].

Question 5

A let obj = {};

B obj.pets = ["Rex", "Mia"];

C console.log(obj.pets.0);

Line C — Use bracket notation obj.pets[0], not a dot, for an array index.

Student with a class code? Join your class →