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. 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}

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

A) Hello

B) "Hello"

C) 'Hello'

D) “Hello”

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

A) [1, 2, null, 4]

B) [1, 2, undefined, 4]

C) Throws a SyntaxError

D) [1, 2, , 4]

4 / 30

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

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

B) Add a spaces property to the JSON object

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

D) Use JSON.prettyPrint()

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5. 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

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6. How can JSON responses be protected from being cached by unauthorized users?

A) Minify the JSON data

B) Convert JSON to XML

C) Use the Cache-Control header with no-store

D) Use large nested objects

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7. Which JavaScript method can convert an object into a JSON string for an API request?

A) JSON.stringify()

B) JSON.serialize()

C) JSON.parse()

D) JSON.encode()

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8. What is used to enclose JSON keys?

A) Parentheses

B) Single quotes

C) Double quotes

D) No quotes

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

A) JSON.compress()

B) JSON.parse()

C) JSON.encode()

D) JSON.stringify()

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

A) The authentication type

B) The client type

C) The server's API version

D) The data format expected in the response

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11. What is the primary role of JSON in GraphQL APIs?

A) To handle authentication

B) To format query results

C) To define the schema

D) To manage subscriptions

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12. What is a safe alternative to eval() for parsing JSON in JavaScript?

A) JSON.minify()

B) JSON.debug()

C) JSON.stringify()

D) JSON.parse()

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13. What does the oneOf keyword do in JSON Schema?

A) Requires all listed schemas to match

B) Validates against one specific type

C) Ensures that the data matches exactly one of the specified schemas

D) Combines multiple schemas

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

A) String

B) Array

C) Number

D) Date

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15. Which tool can convert a JSON file into a different format like CSV?

A) JSONLint

B) JSON Formatter

C) Postman

D) jq

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16. What happens if there is a syntax error in a JSON file?

A) It displays a warning but continues

B) It will fail to parse

C) It gets ignored

D) The JSON file still works

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

A) array.get(1)

B) array.index(1)

C) array[1]

D) array["banana"]

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

A) Returns undefined

B) Throws a TypeError

C) Continues execution without errors

D) Returns an empty object

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19. Which of the following formats can JSON be easily converted into for data visualization?

A) XML

B) HTML

C) All of the above

D) CSV

20 / 30

20. Which of the following best describes JSON?

A) A lightweight data format

B) A programming language

C) A markup language like XML

D) A database system

21 / 30

21. What is the advantage of using JSON in IoT (Internet of Things) devices?

A) It reduces power consumption

B) It is faster than wireless communication

C) It encrypts all data automatically

D) It provides a lightweight and flexible data format

22 / 30

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

A) name

B) "name!"

C) "_name"

D) "123name"

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

A) {"key2": "value"}

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

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

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

24 / 30

24. What does the package.json file in a Node.js project contain?

A) The project's HTML templates

B) A list of all JavaScript files

C) Metadata about the project, dependencies, and scripts

D) The project's CSS styles

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25. Which of the following tools can debug REST API calls and their JSON responses?

A) Notepad++

B) Postman

C) JSONLint

D) Visual Studio Code

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26. How does HTTPS improve the security of JSON data transmission?

A) It beautifies JSON responses

B) It encrypts JSON data in transit

C) It validates JSON schemas

D) It makes JSON larger

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27. Which of the following ensures JSON data is safe from injection attacks?

A) Input validation and sanitization

B) Removing all keys from JSON

C) Minification

D) Using only numeric data

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28. What is the purpose of the dependencies keyword in JSON Schema?

A) To validate nested objects

B) To specify default values

C) To define key dependencies

D) To define type constraints

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29. How does Postman help in debugging JSON APIs?

A) It validates JSON against schemas

B) It converts JSON to XML

C) It beautifies JSON data

D) It sends requests and shows JSON responses

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30. What is the MIME type for JSON?

A) application/json

B) text/json

C) text/plain

D) application/javascript

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