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. What is the default HTTP method for the fetch() function?

A) PUT

B) PATCH

C) GET

D) POST

2 / 30

2. Which of these is valid for a JSON number?

A) 1.23

B) -456

C) 123e5

D) All of the above

3 / 30

3. How can you find the length of an array inside a JSON object?

A) jsonObject.array.size()

B) jsonObject.array.len

C) jsonObject.array.count()

D) jsonObject.array.length

4 / 30

4. Which of the following methods can help trace JSON parsing errors in JavaScript?

A) window.debug()

B) try...catch blocks around JSON.parse()

C) console.parse()

D) JSON.log()

5 / 30

5. Which of these is NOT a valid JSON value?

A) A function

B) A boolean

C) A null value

D) A string

6 / 30

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

A) Functions are converted to strings

B) Functions are ignored

C) Throws an error

D) Adds null in place of functions

7 / 30

7. What happens if a JSON object has circular references when using JSON.stringify()?

A) It returns an empty object

B) It skips the circular reference and continues

C) It converts successfully

D) It throws a TypeError

8 / 30

8. Can JSON keys have spaces?

A) Yes, with quotes

B) Only in arrays

C) No

D) Yes, without quotes

9 / 30

9. What is the default value of additionalProperties in JSON Schema?

A) null

B) false

C) true

D) undefined

10 / 30

10. How does Elasticsearch use JSON?

A) To define relational tables

B) To validate user input

C) To store and query documents

D) To render dashboards

11 / 30

11. What is the correct JSON format for a boolean value?

A) True or False

B) "true" or "false"

C) TRUE or FALSE

D) true or false

12 / 30

12. Which of the following is NOT a valid JSON key?

A) name

B) "_name"

C) "123name"

D) "name!"

13 / 30

13. What is used to enclose JSON keys?

A) Double quotes

B) Single quotes

C) Parentheses

D) No quotes

14 / 30

14. Which of the following is a valid JSON string?

A) “Hello”

B) Hello

C) "Hello"

D) 'Hello'

15 / 30

15. Which of the following is an example of a valid JSON number?

A) 123.45

B) "123"

C) Both B and C

D) 123

16 / 30

16. What happens if you call JSON.stringify() on a Date object?

A) The date is converted to a string in ISO format

B) The date is serialized as a timestamp

C) Throws an error

D) The date is ignored

17 / 30

17. Which character is used to enclose a JSON array?

A) ()

B) <>

C) {}

D) []

18 / 30

18. Which of the following is a valid JSON string?

A) “Hello”

B) 'Hello'

C) Hello

D) "Hello"

19 / 30

19. What is the best approach to log sensitive information within JSON responses?

A) Avoid logging altogether

B) Use JSON.stringify()

C) Log the raw JSON data as is

D) Use a secure logging framework and mask sensitive data

20 / 30

20. Which method is used to convert a JavaScript object into a JSON string?

A) JSON.parse()

B) JSON.toString()

C) JSON.stringify()

D) JSON.encode()

21 / 30

21. 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}

22 / 30

22. What is the difference between allOf and oneOf in JSON Schema?

A) allOf validates all schemas, oneOf validates only one schema

B) allOf allows duplicates, oneOf does not

C) oneOf requires at least one match, allOf requires none

D) allOf is for strings, oneOf is for arrays

23 / 30

23. What does the .eslintrc.json file configure in JavaScript projects?

A) Linting rules and code quality settings

B) Project dependencies

C) Server configurations

D) Database schemas

24 / 30

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

A) To encrypt the request data

B) To authenticate the client

C) To indicate the request priority

D) To specify the API version

25 / 30

25. Which of these is a valid JSON array of strings?

A) ['apple', 'banana', 'cherry']

B) ["apple", 'banana', "cherry"]

C) [apple, banana, cherry]

D) ["apple", "banana", "cherry"]

26 / 30

26. Which of these techniques can prevent excessive JSON data exposure in APIs?

A) Using JSON.stringify()

B) Avoiding nested JSON structures

C) Enabling strict validation in APIs

D) Compressing JSON

27 / 30

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

A) Defines the keys allowed in an object

B) Lists all required fields in an object

C) Specifies the data type of an array

D) Defines the maximum number of keys in an object

28 / 30

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

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

B) An error is thrown

C) The first key-value pair is ignored

D) Both key-value pairs are stored

29 / 30

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

A) To compress JSON

B) To improve parsing speed

C) To prevent unexpected errors and security vulnerabilities

D) To convert JSON into JavaScript objects

30 / 30

30. What is the output of JSON.stringify() on a nested object?

A) Throws an error

B) A flattened version of the object

C) A string representation of the nested object

D) A deep copy of the object

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