JSON Quiz Test Online (30 random Questions) 2025

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 happens if there is a syntax error in a JSON file?

A) It will fail to parse

B) It displays a warning but continues

C) The JSON file still works

D) It gets ignored

2 / 30

2. Which HTTP method is commonly used to fetch JSON data from an API?

A) GET

B) PUT

C) POST

D) DELETE

3 / 30

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

A) True

B) TRUE

C) "true"

D) true

4 / 30

4. How do you specify a pattern for a string in JSON Schema?

A) format

B) match

C) regex

D) pattern

5 / 30

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

A) 'Hello'

B) “Hello”

C) Hello

D) "Hello"

6 / 30

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

A) The HTTP method to be used

B) The size of the request body

C) The status of the response

D) The format of the data being sent or expected

7 / 30

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

A) "Hello"

B) 123

C) null

D) undefined

8 / 30

8. Can JSON keys have spaces?

A) Yes, without quotes

B) No

C) Only in arrays

D) Yes, with quotes

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9. What is the potential issue with using eval() to parse JSON strings in JavaScript?

A) Increased memory usage

B) It cannot parse valid JSON strings

C) Slower parsing

D) Vulnerability to code injection attacks

10 / 30

10. Which of the following is true about JSON numbers?

A) They cannot be negative

B) They support both integers and floats

C) They must be enclosed in double quotes

D) They must include a decimal point

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11. How do you check if a string is valid JSON in JavaScript?

A) Parse it with JSON.parse() inside a try...catch block

B) Use typeof to check its type

C) Use JSON.check()

D) Use JSON.isValid()

12 / 30

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

A) Number

B) Undefined

C) String

D) Boolean

13 / 30

13. Why is it important to remove unused fields from JSON responses?

A) To enhance JSON readability

B) To prevent JSON schema validation errors

C) To avoid key duplication

D) To reduce payload size and improve performance

14 / 30

14. 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

15 / 30

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

A) 1.23f

B) float(1.23)

C) "1.23"

D) 1.23

16 / 30

16. From which programming language is JSON derived?

A) Python

B) JavaScript

C) C++

D) Java

17 / 30

17. What is the purpose of using JSON Web Tokens (JWT)?

A) To replace JSON

B) To validate and secure data transmission

C) To convert JSON into binary format

D) To beautify JSON

18 / 30

18. What is the output of the code: JSON.stringify({ key: undefined, key2: "value" });

A) {"key": undefined, "key2": "value"}

B) {"key2": "value"}

C) {"key": null, "key2": "value"}

D) {"key": "", "key2": "value"}

19 / 30

19. How are multiple key-value pairs separated in a JSON object?

A) Semicolon

B) Dot

C) Comma

D) Hyphen

20 / 30

20. What is the root element of a JSON document?

A) An object or array

B) A number

C) A key-value pair

D) A string

21 / 30

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

A) include

B) required

C) mandatory

D) fields

22 / 30

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

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

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

C) allOf allows duplicates, oneOf does not

D) allOf is for strings, oneOf is for arrays

23 / 30

23. What happens when a fetch() request encounters a network error?

A) Returns an empty object

B) Continues execution without errors

C) Throws a TypeError

D) Returns undefined

24 / 30

24. What does a JSON Formatter do?

A) Formats JSON into a readable and indented structure

B) Compresses JSON into a single line

C) Parses JSON into JavaScript objects

D) Converts JSON to XML

25 / 30

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

A) null

B) undefined

C) none

D) ""

26 / 30

26. Which online tool is commonly used to format JSON for readability?

A) JSONLint

B) Visual Studio Code

C) Postman

D) GitHub

27 / 30

27. What is the most efficient way to handle large JSON datasets in memory-constrained environments?

A) Remove all nested objects

B) Use streaming APIs to process JSON incrementally

C) Convert JSON to XML first

D) Load the entire JSON at once

28 / 30

28. How can you format JSON output with spaces using JSON.stringify()?

A) Use the JSON.stringify(obj, null, 4) method

B) Use JSON.prettyPrint()

C) Add a spaces property to the JSON object

D) Pass a null parameter to JSON.stringify()

29 / 30

29. What is the purpose of the space parameter in JSON.stringify()?

A) To format the output with indentation

B) To add extra spacing between keys and values

C) To compress the JSON output

D) To add a specific number of spaces to the start of the output

30 / 30

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

A) .json

B) .xml

C) .js

D) .txt

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