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.

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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. Can a JSON object be empty?

A) Yes

B) No

C) Only when nested

D) Only in arrays

2 / 30

2. What does the term API stand for?

A) Application Process Integration

B) Automated Programming Integration

C) Advanced Processing Interface

D) Application Programming Interface

3 / 30

3. Which type of JSON structure is most efficient for transmitting data?

A) JSON with comments

B) Flat, simple key-value pairs

C) Deeply nested objects

D) Objects with arrays

4 / 30

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

A) Functions are converted to strings

B) Functions are ignored

C) Adds null in place of functions

D) Throws an error

5 / 30

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

A) null

B) ""

C) []

D) {}

6 / 30

6. What happens when duplicate keys are present in a JSON object?

A) An error is thrown

B) The last key-value pair overrides the previous ones

C) The first key-value pair is ignored

D) Both key-value pairs are stored

7 / 30

7. Which of the following is NOT a valid use case of JSON.stringify()?

A) Formatting JSON output with indentation

B) Serializing objects with circular references

C) Converting JavaScript objects into readable JSON format

D) Serializing objects for storage or transmission

8 / 30

8. How are negative numbers represented in JSON?

A) [123]

B) (123)

C) -123

D) negative123

9 / 30

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

A) The format of a date field

B) The default value of a property

C) A list of allowed values for a property

D) The maximum length of a string

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10. How do you represent a key-value pair where the value is an array?

A) { "key": [ "value1", "value2" ] }

B) { "key": "value1", "value2" }

C) { "key": { "value1": "value2" } }

D) [ { "key": "value1" } ]

11 / 30

11. What will be the result of JSON.stringify([1, 2, 3])?

A) "1,2,3"

B) Throws an error

C) "[1,2,3]"

D) [1, 2, 3]

12 / 30

12. Which messaging protocol often uses JSON for message payloads?

A) FTP

B) POP3

C) MQTT

D) SMTP

13 / 30

13. Which of these is a valid boolean value in JSON?

A) true

B) TRUE

C) "true"

D) True

14 / 30

14. What happens when you use JSON.stringify() on an object with a circular reference?

A) It throws a TypeError

B) It throws a syntax error

C) It converts the object to a string successfully

D) It ignores the circular reference

15 / 30

15. Can JSON arrays contain objects?

A) Only strings

B) Yes

C) Only numbers

D) No

16 / 30

16. What is the purpose of the Authorization header in API requests?

A) To include authentication credentials

B) To specify data format

C) To specify the API version

D) To set request priority

17 / 30

17. What happens if a key in a JSON object contains special characters?

A) The key is ignored

B) It throws an error

C) The key must be enclosed in double quotes

D) The special characters are escaped automatically

18 / 30

18. What does the Content-Type header specify in an API request?

A) The status of the response

B) The HTTP method to be used

C) The size of the request body

D) The format of the data being sent or expected

19 / 30

19. What is the correct syntax for a JSON object?

A) {"key": "value"}

B) {key = "value"}

C) {key: "value"}

D) [key: "value"]

20 / 30

20. Which keyword is used to specify required fields in a JSON object?

A) include

B) fields

C) mandatory

D) required

21 / 30

21. Why is it important to validate JSON data received from external sources?

A) To prevent unexpected errors and security vulnerabilities

B) To improve parsing speed

C) To convert JSON into JavaScript objects

D) To compress JSON

22 / 30

22. What is the purpose of an API key in requests?

A) To encrypt the request data

B) To authenticate the client

C) To specify the API version

D) To indicate the request priority

23 / 30

23. Which method can be used to transform a JSON object into an iterable array?

A) Object.values()

B) Object.entries()

C) All of the above

D) Object.keys()

24 / 30

24. In which cloud service is JSON commonly used for defining infrastructure as code?

A) Microsoft Azure

B) Firebase

C) DigitalOcean

D) Amazon Web Services (AWS) CloudFormation

25 / 30

25. Which of the following files often uses JSON for configuration?

A) config.xml

B) config.txt

C) settings.json

D) preferences.ini

26 / 30

26. What is the result of JSON.parse('null') in JavaScript?

A) Returns undefined

B) Throws a syntax error

C) Returns null

D) Converts to the string "null"

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27. What is the output of JSON.parse('[1, 2, , 4]')?

A) [1, 2, null, 4]

B) [1, 2, , 4]

C) Throws a SyntaxError

D) [1, 2, undefined, 4]

28 / 30

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

A) String

B) Number

C) Array

D) Date

29 / 30

29. How do you reference the parent key in a deeply nested JSON object?

A) Use a library to navigate JSON paths

B) Use parent() function

C) JSON does not support parent references

D) Use key.parent

30 / 30

30. Which of the following JSON values is equivalent to "no value"?

A) null

B) undefined

C) none

D) ""

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