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 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 format of the data being sent or expected

D) The status of the response

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

A) To avoid key duplication

B) To reduce payload size and improve performance

C) To enhance JSON readability

D) To prevent JSON schema validation errors

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

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

B) allOf allows duplicates, oneOf does not

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

D) allOf is for strings, oneOf is for arrays

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

A) array.index(1)

B) array[1]

C) array["banana"]

D) array.get(1)

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

A) Only strings

B) Only objects

C) Only numbers

D) Mixed data types

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6. How can you debug a failing JSON API request in a browser?

A) Validate the response JSON using a linter

B) Check the network tab in developer tools

C) Use console.log for JSON output

D) All of the above

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7. How do you handle errors in a fetch() request?

A) Errors cannot be handled in fetch()

B) Using fetchError() function

C) Using the error property of the response

D) Using try...catch blocks or then().catch() methods

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

A) SQL Injection

B) Remote Code Execution

C) Cross-Site Scripting (XSS)

D) Denial of Service (DoS)

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9. Which of the following best describes JSON?

A) A markup language like XML

B) A database system

C) A programming language

D) A lightweight data format

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

A) [1, 2, undefined, 4]

B) [1, 2, null, 4]

C) Throws a SyntaxError

D) [1, 2, , 4]

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11. How do you represent a null value in JSON?

A) (null)

B) "null"

C) null

D) NULL

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12. Which function can convert an API response from JSON to JavaScript objects?

A) response.parse()

B) JSON.decode()

C) response.json()

D) JSON.stringify()

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13. Which character is used to enclose a JSON array?

A) {}

B) ()

C) []

D) <>

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14. How do you access the value "Alice" from the JSON object {"name": "Alice", "age": 25}?

A) object["Alice"]

B) object[0]

C) object.name

D) object[1]

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

A) 'Hello'

B) "Hello"

C) “Hello”

D) Hello

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16. How is JSON used in microservices architecture?

A) To define database schemas

B) To exchange data between microservices

C) To compile service code

D) To render UI components

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

A) Undefined

B) String

C) Boolean

D) Number

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18. What is JSON primarily used for?

A) Data exchange between a client and a server

B) Styling web pages

C) Sending emails

D) Creating animations

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

A) Array

B) String

C) Number

D) Object

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

A) Array

B) String

C) Null

D) Object

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21. Can JSON values be functions?

A) Only in objects

B) No

C) Only in arrays

D) Yes

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22. Which of these web technologies heavily relies on JSON for communication?

A) WebSockets

B) HTTP/2

C) SOAP

D) GraphQL

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

A) Slower parsing

B) Vulnerability to code injection attacks

C) Increased memory usage

D) It cannot parse valid JSON strings

24 / 30

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

A) SyntaxError: Unexpected token

B) Missing property name

C) Undefined object

D) Invalid JSON

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25. Which HTTP header is critical for securing JSON responses?

A) Content-Type

B) X-Content-Type-Options

C) Access-Control-Allow-Origin

D) Accept-Encoding

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

A) maxSize

B) minLength

C) arrayLimit

D) maxItems

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

A) All of the above

B) Object

C) Float

D) String

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28. Which of the following JSON strings can be parsed without error?

A) '{"name": "John", "age": 30}'

B) '{name: "John", age: 30}'

C) '{name: John, age: 30}'

D) '{"name": John, "age": 30}'

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

A) properties: []

B) additionalFields: false

C) additionalProperties: false

D) maxProperties: 0

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30. Can a JSON object have duplicate keys?

A) Yes

B) No

C) Only in nested objects

D) Only in arrays

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