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.

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1. Which of the following is NOT a valid use case of JSON.stringify()?

A) Serializing objects with circular references

B) Formatting JSON output with indentation

C) Serializing objects for storage or transmission

D) Converting JavaScript objects into readable JSON format

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

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

B) Minify the JSON data

C) Convert JSON to XML

D) Use large nested objects

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3. What happens if a key in a JSON object contains special characters?

A) The special characters are escaped automatically

B) The key must be enclosed in double quotes

C) It throws an error

D) The key is ignored

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

A) Hello

B) “Hello”

C) 'Hello'

D) "Hello"

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5. What is the output of response.ok in a fetch() API call if the request is successful?

A) 1

B) true

C) null

D) "ok"

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6. How does JSON web encryption (JWE) enhance JSON security?

A) It converts JSON to binary format

B) It compresses JSON data

C) It encrypts JSON payloads for secure transmission

D) It adds authentication to JSON

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

A) To convert JSON into JavaScript objects

B) To compress JSON

C) To prevent unexpected errors and security vulnerabilities

D) To improve parsing speed

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8. What does the enum keyword specify in JSON Schema?

A) The default value of a property

B) A list of allowed values for a property

C) The format of a date field

D) The maximum length of a string

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9. Which of the following tools allows real-time collaboration on JSON data?

A) JSON Editor Online

B) JSONLint

C) Google Docs

D) JIRA

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10. JSON is a strict subset of which language?

A) JavaScript

B) XML

C) Python

D) SQL

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

A) All of the above

B) 123e5

C) 1.23

D) -456

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

A) Database schemas

B) Server configurations

C) Linting rules and code quality settings

D) Project dependencies

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13. How can large nested JSON objects impact performance?

A) They slow down parsing and increase memory usage

B) They make JSON more secure

C) They improve network speed

D) They reduce API latency

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

A) Load the entire JSON object in memory

B) Use streaming parsers like JSONStream

C) Split the JSON file into multiple smaller files

D) Both B and C

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15. What is the purpose of JSON in REST APIs?

A) To define API endpoints

B) To structure and exchange data between client and server

C) To render HTML pages

D) To validate API responses

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16. Which of the following data types can JSON arrays contain?

A) Mixed data types

B) Only objects

C) Only numbers

D) Only strings

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

A) .json

B) .js

C) .xml

D) .txt

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18. Which database natively supports JSON as its data format?

A) MySQL

B) SQLite

C) PostgreSQL

D) MongoDB

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19. How can you handle errors when parsing JSON in JavaScript?

A) Using a try...catch block

B) Using the JSON.validate() method

C) Checking the JSON string with isValid()

D) JSON parsing cannot produce errors

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

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

B) {"key2": "value"}

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

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

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

A) Semicolon (;)

B) Comma (,)

C) Colon (:)

D) Equal sign (=)

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

A) Object

B) String

C) Float

D) All of the above

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23. Can JSON values be functions?

A) Yes

B) No

C) Only in arrays

D) Only in objects

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

A) Null

B) Array

C) String

D) Object

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

A) range

B) minimum and maximum

C) numberRange

D) min and max

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

A) Returns an empty object

B) Continues execution without errors

C) Returns undefined

D) Throws a TypeError

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27. Can JSON objects contain duplicate keys?

A) Yes, but only for strings

B) No

C) Yes, the last key-value pair overrides the previous ones

D) Yes, with an error

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28. What is the result of JSON.parse('null') in JavaScript?

A) Returns undefined

B) Throws a syntax error

C) Returns null

D) Converts to the string "null"

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

A) Enabling strict validation in APIs

B) Using JSON.stringify()

C) Avoiding nested JSON structures

D) Compressing JSON

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30. How does Postman help in debugging JSON APIs?

A) It validates JSON against schemas

B) It sends requests and shows JSON responses

C) It beautifies JSON data

D) It converts JSON to XML

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