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 used to enclose JSON keys?

A) Parentheses

B) Double quotes

C) No quotes

D) Single quotes

2 / 30

2. Which attack can occur when JSON data is excessively large and causes resource exhaustion?

A) Denial of Service (DoS)

B) SQL Injection

C) Remote Code Execution

D) Cross-Site Scripting (XSS)

3 / 30

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

A) [1, 2, null, 4]

B) Throws a SyntaxError

C) [1, 2, undefined, 4]

D) [1, 2, , 4]

4 / 30

4. Which JSON data type is used to group key-value pairs?

A) Object

B) String

C) Array

D) Number

5 / 30

5. Why should you limit the depth of nested JSON objects?

A) To prevent DoS attacks caused by deep recursion

B) To reduce data size

C) To improve readability

D) To remove duplicate keys

6 / 30

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

A) properties: []

B) additionalProperties: false

C) additionalFields: false

D) maxProperties: 0

7 / 30

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

A) JSONLint

B) Static analysis tools or manual comparison

C) JSON Formatter

D) Postman

8 / 30

8. Can JSON values be functions?

A) Yes

B) Only in objects

C) Only in arrays

D) No

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9. Which testing tools commonly use JSON for request and response data?

A) Postman and JMeter

B) Figma and Sketch

C) Selenium and Puppeteer

D) Jenkins and Kubernetes

10 / 30

10. How is JSON used in data interchange for machine learning models?

A) To compile machine learning libraries

B) To serialize model configurations and results

C) To train models directly

D) To render visualizations

11 / 30

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

A) A string

B) An object or array

C) A key-value pair

D) A number

12 / 30

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

A) Deeply nested objects

B) Objects with arrays

C) Flat, simple key-value pairs

D) JSON with comments

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 does the term API stand for?

A) Advanced Processing Interface

B) Application Programming Interface

C) Application Process Integration

D) Automated Programming Integration

15 / 30

15. How do you access the second element of a JSON array ["apple", "banana", "cherry"]?

A) array["banana"]

B) array.get(1)

C) array[1]

D) array.index(1)

16 / 30

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

A) [key: "value"]

B) {"key": "value"}

C) {key = "value"}

D) {key: "value"}

17 / 30

17. Which keyword restricts the number of items in a JSON array?

A) maxItems

B) arrayLimit

C) maxSize

D) minLength

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18. Which of the following is an invalid JSON structure?

A) { "key": "value", "key": "anotherValue" }

B) [ { "key1": "value1" }, { "key2": "value2" } ]

C) { "key": { "nested": { "deep": [1, 2] } } }

D) { "key": [1, 2, { "nested": "value" }] }

19 / 30

19. What data type is represented by {} in JSON?

A) Object

B) String

C) Null

D) Array

20 / 30

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

A) Converts to an empty object

B) Skips invalid parts

C) Returns null

D) Throws a SyntaxError

21 / 30

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

A) 1.23

B) 1.23f

C) "1.23"

D) float(1.23)

22 / 30

22. How can large nested JSON objects impact performance?

A) They slow down parsing and increase memory usage

B) They reduce API latency

C) They make JSON more secure

D) They improve network speed

23 / 30

23. Which of the following status codes indicates a successful API request?

A) 404

B) 500

C) 200

D) 403

24 / 30

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

A) It ignores the circular reference

B) It throws a TypeError

C) It throws a syntax error

D) It converts the object to a string successfully

25 / 30

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

A) PATCH

B) GET

C) PUT

D) POST

26 / 30

26. How do you handle very large JSON data efficiently in JavaScript?

A) Split the JSON file into multiple smaller files

B) Use streaming parsers like JSONStream

C) Both B and C

D) Load the entire JSON object in memory

27 / 30

27. What separates two key-value pairs in a JSON object?

A) Hyphen

B) Colon

C) Comma

D) Semicolon

28 / 30

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

A) "Hello"

B) Hello

C) “Hello”

D) 'Hello'

29 / 30

29. What error does a missing comma between JSON key-value pairs produce?

A) SyntaxError: Unexpected token

B) Undefined object

C) Invalid JSON

D) Missing property name

30 / 30

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

A) [1, 2, "three"]

B) [1; 2; 3]

C) (1, 2, 3)

D) {"1", "2", "3"}

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