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. How do you access the name of the first employee in the JSON structure { "department": { "employees": [ { "name": "John" }, { "name": "Alice" } ] } }?

A) department.employees[1].name

B) department[employees][name]

C) employees[0].name

D) department.employees[0].name

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2. What is the purpose of the fetch() method in JavaScript?

A) To parse JSON strings

B) To send emails

C) To encrypt data

D) To make HTTP requests to APIs

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

A) “Hello”

B) "Hello"

C) 'Hello'

D) Hello

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4. Which HTTP method is typically used for sending data to an API?

A) GET

B) DELETE

C) POST

D) OPTIONS

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

A) Minification

B) Removing all keys from JSON

C) Using only numeric data

D) Input validation and sanitization

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

A) To improve parsing speed

B) To prevent unexpected errors and security vulnerabilities

C) To convert JSON into JavaScript objects

D) To compress JSON

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7. Which of these is NOT allowed in JSON arrays?

A) Nested arrays

B) Objects as elements

C) Mixed data types

D) Functions as elements

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8. What can be the root structure of a JSON document?

A) Only an object

B) A string

C) Only an array

D) Either an object or an array

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

A) pattern

B) regex

C) match

D) format

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

A) Comma (,)

B) Colon (:)

C) Equal sign (=)

D) Semicolon (;)

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11. What is used to enclose JSON keys?

A) Double quotes

B) No quotes

C) Single quotes

D) Parentheses

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12. Which JSON data type is used to represent a collection of items?

A) String

B) Number

C) Object

D) Array

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13. Which tool is used to validate JSON syntax?

A) JSONLint

B) XMLParser

C) Postman

D) JSONParser

14 / 30

14. What is a common use of JSON in mobile applications?

A) Managing memory allocation

B) Exchanging data with remote APIs

C) Defining app layouts

D) Compiling source code

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

A) It throws an error

B) The special characters are escaped automatically

C) The key is ignored

D) The key must be enclosed in double quotes

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

A) To structure and exchange data between client and server

B) To validate API responses

C) To define API endpoints

D) To render HTML pages

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

A) Only objects

B) Only numbers

C) Only strings

D) Mixed data types

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18. What type of data does a JSON object contain?

A) Only text

B) Only numbers

C) Only arrays

D) Key-value pairs

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

A) minimum and maximum

B) numberRange

C) range

D) min and max

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20. What is the best approach to log sensitive information within JSON responses?

A) Use JSON.stringify()

B) Use a secure logging framework and mask sensitive data

C) Avoid logging altogether

D) Log the raw JSON data as is

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21. How can large nested JSON objects impact performance?

A) They slow down parsing and increase memory usage

B) They reduce API latency

C) They improve network speed

D) They make JSON more secure

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22. Which keyword in JSON Schema defines the type of a value?

A) properties

B) items

C) format

D) type

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

A) It gets ignored

B) It will fail to parse

C) It displays a warning but continues

D) The JSON file still works

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24. Which of the following is the correct way to represent an empty JSON object?

A) null

B) ""

C) {}

D) []

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

A) undefined

B) null

C) ""

D) none

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

A) maxItems

B) maxSize

C) minLength

D) arrayLimit

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27. Which of these is NOT a valid JSON value?

A) A null value

B) A string

C) A boolean

D) A function

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28. How do you represent a key-value pair where the value is an array?

A) [ { "key": "value1" } ]

B) { "key": [ "value1", "value2" ] }

C) { "key": "value1", "value2" }

D) { "key": { "value1": "value2" } }

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29. How do you check if a given JavaScript object is a valid JSON object?

A) Use Array.isArray()

B) Use typeof to check if it is an object

C) Use Object.prototype.toString()

D) Convert it to a string using JSON.stringify() and back using JSON.parse()

30 / 30

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

A) It compresses JSON data

B) It adds authentication to JSON

C) It converts JSON to binary format

D) It encrypts JSON payloads for secure transmission

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