Nested Arrays and Objects
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Does person.pets[0] access an element nested inside an object?
2. Can dot notation and bracket notation be chained together?
3. Does grid[0][1] access an element in a 2D array?
4. Is users.0.name valid syntax for accessing an array element?
5. Does obj.addr.city access a property nested two levels deep?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1obj.pets[0] | AAccesses the city property nested inside addr inside obj | |
| 2obj.addr.city | BWrong - a nested property needs a dot, not unquoted brackets | |
| 3Accesses an element in a 2D array using two indexes | Cusers[0].name | |
| 4Accesses a property on an object stored inside an array | DWrong - array indexes use brackets, not dots | |
| 5users.0.name | Egrid[0][1] | |
| 6obj.addr[city] | FAccesses the first element of the pets array inside obj |
C
Definitions
obj.pets[0]
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
console.log(person.pets_0]);
2.
console.log(obj.addr_city);
3.
console.log(users[0]_name);
4.
console.log(data.scores[_]);
5.
console.log(grid[0]_1]);
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
console.log(objpets[0]);
B
let obj = {};
C
obj.pets = ["Rex", "Mia"];
Question 2
A
objaddr = {city: "NYC"};
B
let obj = {};
C
console.log(obj.addr.city);
Question 3
A
let obj = {};
B
obj.pets = ("Rex", "Mia");
C
console.log(obj.pets[0]);
Question 4
A
let obj = {};
B
obj.addr = {city: "NYC"];
C
console.log(obj.addr.city);
Question 5
A
let obj = {};
B
obj.pets = ["Rex", "Mia"];
C
console.log(obj.pets.0);
Answer Key
Nested Arrays and Objects
Section A: Quick Questions
Q1
B — Yes
Q2
A — Yes
Q3
B — Yes
Q4
A — No
Q5
A — Yes
Section B: Match the Pairs
Q1
obj.pets[0] → Accesses the first element of the pets array inside obj
Q2
obj.addr.city → Accesses the city property nested inside addr inside obj
Q3
Accesses an element in a 2D array using two indexes → grid[0][1]
Q4
Accesses a property on an object stored inside an array → users[0].name
Q5
users.0.name → Wrong - array indexes use brackets, not dots
Q6
obj.addr[city] → Wrong - a nested property needs a dot, not unquoted brackets
Section C: Definitions
Q1
obj.pets[0] — Chains dot notation and bracket notation to access a value nested inside an object.Section D: Fill in the Blanks
Q1
console.log(person.pets[0]);Q2
console.log(obj.addr.city);Q3
console.log(users[0].name);Q4
console.log(data.scores[2]);Q5
console.log(grid[0][1]);Section E: Spot the Error
Q1
A — Missing the dot before pets - it should be obj.pets[0].
Q2
A — Missing the dot before addr - it should be obj.addr.
Q3
B — Arrays use square brackets [], not round brackets ().
Q4
B — Object literals close with }, not ].
Q5
C — Use bracket notation obj.pets[0], not a dot, for an array index.