JSON Quiz Test Online (30 random Questions) 2026

This quick 30-minute challenge consists of 30 random multiple-choice questions designed to test your knowledge across various JSON topics, including the introduction to JSON, JSON syntax and basics, data types, operations in JavaScript, APIs and JSON, advanced structures, JSON Schema, tools and debugging, as well as performance and security considerations. Whether you’re new to JSON or looking to refine your skills, this quiz will enhance your understanding of JSON’s role in modern web development.

0 votes, 0 avg

You have 30 minutes to complete the quiz. The timer will start when you click the 'Start Quiz' button. Please ensure you are ready before beginning.

Time is up! Your quiz has ended. Your responses have been submitted automatically.

30 Minutes JSON Quiz Test Online

Welcome to the JSON Quiz! This quick 30-minute challenge consists of 30 random multiple-choice questions designed to test your knowledge across various JSON topics, including the introduction to JSON, JSON syntax and basics, data types, operations in JavaScript, APIs and JSON, advanced structures, JSON Schema, tools and debugging, as well as performance and security considerations. Whether you're new to JSON or looking to refine your skills, this quiz will enhance your understanding of JSON's role in modern web development.

1 / 30

1. How do you represent a null value in JSON?

A) null

B) (null)

C) "null"

D) NULL

2 / 30

2. Which of the following values is not valid in JSON?

A) null

B) undefined

C) "Hello"

D) 123

3 / 30

3. How do you validate that a JSON object has no additional fields?

A) additionalProperties: false

B) maxProperties: 0

C) properties: []

D) additionalFields: false

4 / 30

4. Which of the following is the correct JSON format for a key-value pair?

A) {key = value}

B) {"key": value}

C) {"key": "value"}

D) {key: value}

5 / 30

5. Which of the following is the correct way to represent an empty JSON object?

A) []

B) null

C) {}

D) ""

6 / 30

6. Which of the following values can be used as JSON keys?

A) Strings and numbers

B) Strings and booleans

C) Any data type

D) Strings only

7 / 30

7. What will be the output of the code: JSON.stringify({ key1: "value1", key2: function() { return "value2"; } });

A) Throws an error

B) {"key1": "value1"}

C) {"key1": "value1", "key2": null}

D) {"key1": "value1", "key2": "value2"}

8 / 30

8. What happens when you pass a replacer function to JSON.stringify()?

A) It filters the properties to be included in the JSON string

B) It validates the JSON string

C) Throws an error if the function is invalid

D) It ensures all properties are stringified

9 / 30

9. Why should large JSON files be paginated in APIs?

A) To avoid key duplication

B) To improve network performance and reduce latency

C) To reduce client-side processing time

D) To increase readability

10 / 30

10. What is the result of trying to access a non-existent key in a JSON object?

A) Returns null

B) Throws an error

C) Returns an empty string

D) Returns undefined

11 / 30

11. What does the enum keyword specify in JSON Schema?

A) The maximum length of a string

B) A list of allowed values for a property

C) The format of a date field

D) The default value of a property

12 / 30

12. How does JSON.stringify() handle functions in objects?

A) Throws an error

B) Functions are ignored

C) Adds null in place of functions

D) Functions are converted to strings

13 / 30

13. Which of the following is NOT a valid JSON data type?

A) Date

B) String

C) Array

D) Number

14 / 30

14. Which of these is a valid JSON object?

A) {name: "John", age: 30}

B) {name = "John"; age = 30}

C) {"name": "John", "age": 30}

D) [name: "John", age: 30]

15 / 30

15. How can you identify unused keys in a JSON object?

A) Postman

B) Static analysis tools or manual comparison

C) JSONLint

D) JSON Formatter

16 / 30

16. Which of the following is a valid JSON array?

A) {[1, 2, 3]}

B) [1, 2, 3]

C) <1, 2, 3>

D) (1, 2, 3)

17 / 30

17. What is the typical file extension for JSON files?

A) .json

B) .xml

C) .txt

D) .js

18 / 30

18. How does HTTPS improve the security of JSON data transmission?

A) It validates JSON schemas

B) It encrypts JSON data in transit

C) It makes JSON larger

D) It beautifies JSON responses

19 / 30

19. What does the package.json file in a Node.js project contain?

A) The project's CSS styles

B) A list of all JavaScript files

C) The project's HTML templates

D) Metadata about the project, dependencies, and scripts

20 / 30

20. What is the output of response.ok in a fetch() API call if the request is successful?

A) true

B) "ok"

C) null

D) 1

21 / 30

21. What is the purpose of application/json MIME type?

A) To convert JSON to XML

B) To define JSON structure

C) To identify JSON data format

D) To parse JSON

22 / 30

22. What does the properties keyword do in JSON Schema?

A) Specifies the data type of an array

B) Lists all required fields in an object

C) Defines the maximum number of keys in an object

D) Defines the keys allowed in an object

23 / 30

23. Which of the following is NOT a supported data type in JSON?

A) Number

B) Undefined

C) String

D) Boolean

24 / 30

24. What is the result of running JSON.parse('{"key":value}') in JavaScript?

A) A key-value pair object

B) SyntaxError: Unexpected identifier

C) null

D) ReferenceError

25 / 30

25. Can a JSON object be empty?

A) No

B) Only when nested

C) Yes

D) Only in arrays

26 / 30

26. Which of the following is NOT a JSON data type?

A) Date

B) Boolean

C) String

D) Null

27 / 30

27. Which of the following is used to validate the syntax of JSON data?

A) JSON Compressor

B) JSON Beautifier

C) JSON Validator

D) JSON Formatter

28 / 30

28. What is a safe alternative to eval() for parsing JSON in JavaScript?

A) JSON.stringify()

B) JSON.minify()

C) JSON.parse()

D) JSON.debug()

29 / 30

29. What is the output of JSON.stringify([1, undefined, 2])?

A) "[1, , 2]"

B) Throws a TypeError

C) "[1, null, 2]"

D) "[1, undefined, 2]"

30 / 30

30. How does Postman help in debugging JSON APIs?

A) It sends requests and shows JSON responses

B) It validates JSON against schemas

C) It beautifies JSON data

D) It converts JSON to XML

Your score is

The average score is 40%

Rate Your Experience!

Anonymous feedback

Thank you for your feedback! We appreciate your input.

CSS Quiz Test Online (30 random Questions)

HTML Quiz Test Online

10 Minutes JSON Quiz Test Online

10 Minutes Docker Quiz Test Online

MongoDB Quiz Test Online (30 random Questions)

JavaScript Quiz Test Online (30 random Questions)

Related