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 does JSON stand for?

A) Java Syntax Object Notation

B) Java Online Syntax Network

C) JavaScript Object Notation

D) JavaScript Online Network

2 / 30

2. What does the type keyword accept for mixed data types?

A) A boolean flag

B) A numeric range

C) A single string

D) An array of types

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

A) ()

B) []

C) <>

D) {}

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

A) All of the above

B) String

C) Object

D) Float

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5. Can JSON objects be nested inside other JSON objects?

A) Only with strings

B) Yes

C) Only with arrays

D) No

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6. How does JSON.stringify() handle functions in objects?

A) Throws an error

B) Functions are ignored

C) Adds null in place of functions

D) Functions are converted to strings

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7. Which of these is a valid boolean value in JSON?

A) TRUE

B) true

C) "true"

D) True

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8. Can JSON values be functions?

A) No

B) Only in arrays

C) Yes

D) Only in objects

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9. Which of the following is NOT valid in JSON?

A) Comments

B) Numbers

C) Strings

D) Boolean values

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

A) Objects as elements

B) Nested arrays

C) Functions as elements

D) Mixed data types

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11. How do you merge two JSON objects?

A) Use array.push()

B) Use JSON.merge()

C) Use JSON.stringify()

D) Use Object.assign()

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12. What is the default value of additionalProperties in JSON Schema?

A) null

B) true

C) undefined

D) false

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13. How do you specify that a JSON object must have at least one key in JSON Schema?

A) minKeys: 1

B) minProperties: 1

C) minItems: 1

D) required: true

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

A) JSON.parse()

B) JSON.compress()

C) JSON.stringify()

D) JSON.encode()

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15. What does the JSON.parse() method do in JavaScript?

A) Converts a JSON string into a JavaScript object

B) Parses a JSON string into an XML object

C) Validates a JSON string

D) Converts a JavaScript object into a JSON string

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

A) Deeply nested objects

B) Flat, simple key-value pairs

C) JSON with comments

D) Objects with arrays

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17. What will JSON.stringify({ key: undefined }) return?

A) {"key": null}

B) {}

C) {"key": "undefined"}

D) Throws an error

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

A) JSONLint

B) JSON Editor Online

C) Google Docs

D) JIRA

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19. What is the purpose of using JSON Web Tokens (JWT)?

A) To validate and secure data transmission

B) To beautify JSON

C) To convert JSON into binary format

D) To replace JSON

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20. Which keyword is used to specify required fields in a JSON object?

A) required

B) include

C) fields

D) mandatory

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

A) To encrypt data

B) To parse JSON strings

C) To make HTTP requests to APIs

D) To send emails

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22. Which method can be used to transform a JSON object into an iterable array?

A) Object.keys()

B) Object.values()

C) All of the above

D) Object.entries()

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23. Can a JSON object have duplicate keys?

A) No

B) Yes

C) Only in nested objects

D) Only in arrays

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

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

B) Use JSON.prettyPrint()

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

D) Add a spaces property to the JSON object

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26. What does the Content-Security-Policy header do for JSON responses?

A) Restricts where JSON can be loaded from to prevent cross-site scripting (XSS) attacks

B) Defines the format of JSON data

C) Ensures JSON is minified

D) Specifies how JSON is cached

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27. What happens if a JSON object has circular references when using JSON.stringify()?

A) It throws a TypeError

B) It skips the circular reference and continues

C) It converts successfully

D) It returns an empty object

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

A) Cross-Site Scripting (XSS)

B) SQL Injection

C) Remote Code Execution

D) Denial of Service (DoS)

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29. What is the most efficient way to handle large JSON datasets in memory-constrained environments?

A) Remove all nested objects

B) Use streaming APIs to process JSON incrementally

C) Convert JSON to XML first

D) Load the entire JSON at once

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

A) Returns undefined

B) Continues execution without errors

C) Throws a TypeError

D) Returns an empty object

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