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 correct syntax for a JSON object?

A) [key: "value"]

B) {"key": "value"}

C) {key: "value"}

D) {key = "value"}

2 / 30

2. What happens when you use JSON.parse() on an invalid JSON string?

A) Skips invalid parts

B) Converts to an empty object

C) Returns null

D) Throws a SyntaxError

3 / 30

3. Which of the following JSON data types is valid?

A) String

B) All of the above

C) Float

D) Object

4 / 30

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

A) [1, 2, undefined, 4]

B) [1, 2, , 4]

C) [1, 2, null, 4]

D) Throws a SyntaxError

5 / 30

5. Which extension helps debug JSON in Visual Studio Code?

A) JSON Formatter

B) Prettier

C) JSON Tools

D) REST Client

6 / 30

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

A) Project dependencies

B) Server configurations

C) Linting rules and code quality settings

D) Database schemas

7 / 30

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

A) To identify JSON data format

B) To convert JSON to XML

C) To define JSON structure

D) To parse JSON

8 / 30

8. Which JavaScript function converts JSON data into a format suitable for POST requests?

A) JSON.encode()

B) JSON.compress()

C) JSON.stringify()

D) JSON.parse()

9 / 30

9. Which keyword defines a numeric range in JSON Schema?

A) min and max

B) range

C) numberRange

D) minimum and maximum

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10. Can JSON arrays contain objects?

A) Only strings

B) Yes

C) Only numbers

D) No

11 / 30

11. What does the Accept header specify in an API request?

A) The data format expected in the response

B) The authentication type

C) The client type

D) The server's API version

12 / 30

12. What is one method to detect changes in JSON data?

A) Using nested structures

B) Removing whitespace from JSON

C) Hashing the JSON content

D) Beautifying the JSON

13 / 30

13. What is JSON primarily used for?

A) Sending emails

B) Data exchange between a client and a server

C) Styling web pages

D) Creating animations

14 / 30

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

A) To set request priority

B) To specify data format

C) To include authentication credentials

D) To specify the API version

15 / 30

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

A) 123e5

B) -456

C) 1.23

D) All of the above

16 / 30

16. Can a JSON object have duplicate keys?

A) No

B) Only in nested objects

C) Yes

D) Only in arrays

17 / 30

17. How do you merge two JSON objects?

A) Use JSON.stringify()

B) Use Object.assign()

C) Use array.push()

D) Use JSON.merge()

18 / 30

18. How are floating-point numbers represented in JSON?

A) 1.23

B) float(1.23)

C) "1.23"

D) 1.23f

19 / 30

19. What does a JSON compressor do?

A) Validates JSON

B) Removes unnecessary whitespace for smaller size

C) Beautifies JSON

D) Converts JSON to XML

20 / 30

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

A) It throws a TypeError

B) It converts the object to a string successfully

C) It ignores the circular reference

D) It throws a syntax error

21 / 30

21. 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]

22 / 30

22. Can a JSON key have a number as its name?

A) Only in arrays

B) Yes, with quotes

C) No

D) Yes, without quotes

23 / 30

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

A) To prevent unexpected errors and security vulnerabilities

B) To compress JSON

C) To improve parsing speed

D) To convert JSON into JavaScript objects

24 / 30

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

A) "[1, undefined, 2]"

B) Throws a TypeError

C) "[1, , 2]"

D) "[1, null, 2]"

25 / 30

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

A) A deep copy of the object

B) A string representation of the nested object

C) A flattened version of the object

D) Throws an error

26 / 30

26. How can you validate JSON in a secure and efficient way?

A) Use a JSON Schema validator

B) Ignore validation for trusted sources

C) Manually check the JSON

D) Use custom regular expressions

27 / 30

27. What is used to enclose JSON keys?

A) No quotes

B) Single quotes

C) Double quotes

D) Parentheses

28 / 30

28. Can JSON keys have spaces?

A) Only in arrays

B) Yes, with quotes

C) No

D) Yes, without quotes

29 / 30

29. How does Firebase use JSON?

A) For real-time database storage and synchronization

B) To manage authentication tokens

C) To render user interfaces

D) To define cloud functions

30 / 30

30. 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

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