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 is JSON used in data interchange for machine learning models?

A) To render visualizations

B) To serialize model configurations and results

C) To train models directly

D) To compile machine learning libraries

2 / 30

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

A) Adds null in place of functions

B) Throws an error

C) Functions are ignored

D) Functions are converted to strings

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3. 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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4. What is the use of the $ref keyword in JSON Schema?

A) To define a default value

B) To reference external files

C) To include reusable schema definitions

D) To specify required properties

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5. Which of the following is an example of a valid JSON number?

A) 123

B) "123"

C) Both B and C

D) 123.45

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6. 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) employees[0].name

C) department[employees][name]

D) department.employees[0].name

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7. Which data structure is JSON closest to?

A) Relational tables

B) Key-value store

C) Trees

D) Arrays

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

A) 'Hello'

B) “Hello”

C) Hello

D) "Hello"

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9. JSON is _______________.

A) Case-sensitive

B) Partially case-sensitive

C) None of the above

D) Case-insensitive

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10. How does Firebase use JSON?

A) To define cloud functions

B) To render user interfaces

C) To manage authentication tokens

D) For real-time database storage and synchronization

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11. What separates two key-value pairs in a JSON object?

A) Semicolon

B) Comma

C) Hyphen

D) Colon

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

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

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

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

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

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

A) It converts successfully

B) It throws a TypeError

C) It returns an empty object

D) It skips the circular reference and continues

14 / 30

14. What is a common vulnerability associated with parsing untrusted JSON?

A) JSON Brute Force

B) JSON Injection

C) JSON Flooding

D) JSON Parsing Loops

15 / 30

15. What is JSON Schema?

A) A library to parse JSON data

B) A specification to define and validate the structure of JSON data

C) A format to store JSON data

D) A method to minify JSON files

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

A) Semicolon

B) Hyphen

C) Comma

D) Dot

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

A) null

B) 1

C) true

D) "ok"

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18. Which of the following best describes JSON?

A) A markup language like XML

B) A programming language

C) A lightweight data format

D) A database system

19 / 30

19. 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}'

20 / 30

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

A) Compiling source code

B) Exchanging data with remote APIs

C) Managing memory allocation

D) Defining app layouts

21 / 30

21. What is the correct JSON format for a boolean value?

A) true or false

B) TRUE or FALSE

C) True or False

D) "true" or "false"

22 / 30

22. Which of the following is a commonly used library for making API requests in JavaScript?

A) D3.js

B) Axios

C) Lodash

D) jQuery

23 / 30

23. What is used to enclose JSON keys?

A) Parentheses

B) No quotes

C) Single quotes

D) Double quotes

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

A) [1, 2, , 4]

B) [1, 2, null, 4]

C) [1, 2, undefined, 4]

D) Throws a SyntaxError

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

A) []

B) {}

C) null

D) ""

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26. What does JSON stand for?

A) JavaScript Online Network

B) Java Online Syntax Network

C) Java Syntax Object Notation

D) JavaScript Object Notation

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27. How are floating-point numbers represented in JSON?

A) "1.23"

B) 1.23f

C) float(1.23)

D) 1.23

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28. What does the term API stand for?

A) Application Process Integration

B) Application Programming Interface

C) Advanced Processing Interface

D) Automated Programming Integration

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

A) Accept-Encoding

B) Access-Control-Allow-Origin

C) X-Content-Type-Options

D) Content-Type

30 / 30

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

A) JSON.stringify()

B) JSON.parse()

C) JSON.encode()

D) JSON.compress()

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