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. Which tool can convert a JSON file into a different format like CSV?

A) Postman

B) jq

C) JSON Formatter

D) JSONLint

2 / 30

2. How do you deep clone a JSON-compatible object in JavaScript?

A) Use Object.assign()

B) Use JSON.clone()

C) Use the clone() method

D) Use JSON.stringify() and JSON.parse()

3 / 30

3. What does the package.json file in a Node.js project contain?

A) Metadata about the project, dependencies, and scripts

B) The project's CSS styles

C) A list of all JavaScript files

D) The project's HTML templates

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4. Which data structure is not directly supported by JSON?

A) Array

B) Object

C) Set

D) String

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5. How does Firebase use JSON?

A) To define cloud functions

B) To manage authentication tokens

C) For real-time database storage and synchronization

D) To render user interfaces

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6. Can JSON arrays contain objects?

A) No

B) Yes

C) Only numbers

D) Only strings

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

A) "ok"

B) null

C) 1

D) true

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8. How does Elasticsearch use JSON?

A) To define relational tables

B) To render dashboards

C) To validate user input

D) To store and query documents

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9. Which of the following is an example of a nested JSON object?

A) [ "John", 30 ]

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

C) { "name": "John" }

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

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10. Which of the following best describes JSON?

A) A programming language

B) A lightweight data format

C) A markup language like XML

D) A database system

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11. Which keyword specifies the schema for items in a JSON array?

A) type

B) items

C) definitions

D) properties

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12. Which data structure is JSON closest to?

A) Arrays

B) Relational tables

C) Trees

D) Key-value store

13 / 30

13. What is the result of running JSON.parse('{"key":value}') in JavaScript?

A) null

B) ReferenceError

C) SyntaxError: Unexpected identifier

D) A key-value pair object

14 / 30

14. Which of the following is the correct JSON format for a key-value pair?

A) {key: value}

B) {"key": "value"}

C) {key = value}

D) {"key": value}

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

A) float(1.23)

B) 1.23

C) 1.23f

D) "1.23"

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

A) object["Alice"]

B) object.name

C) object[1]

D) object[0]

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

A) MySQL

B) SQLite

C) PostgreSQL

D) MongoDB

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18. 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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19. How are elements in a JSON array separated?

A) Semicolons

B) Commas

C) Colons

D) Dots

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20. What is the primary role of JSON in GraphQL APIs?

A) To define the schema

B) To format query results

C) To handle authentication

D) To manage subscriptions

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21. What will JSON.stringify(true) return?

A) true

B) Throws an error

C) "true"

D) "True"

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

A) array.index(1)

B) array.get(1)

C) array["banana"]

D) array[1]

23 / 30

23. 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

24 / 30

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

A) Functions as elements

B) Objects as elements

C) Mixed data types

D) Nested arrays

25 / 30

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

A) {}

B) ()

C) []

D) <>

26 / 30

26. What is the default HTTP method for the fetch() function?

A) POST

B) PUT

C) PATCH

D) GET

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27. From which programming language is JSON derived?

A) JavaScript

B) Java

C) Python

D) C++

28 / 30

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

A) It returns an empty object

B) It converts successfully

C) It throws a TypeError

D) It skips the circular reference and continues

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

A) Removing all keys from JSON

B) Using only numeric data

C) Input validation and sanitization

D) Minification

30 / 30

30. Which of the following formats can JSON be easily converted into for data visualization?

A) XML

B) HTML

C) CSV

D) All of the above

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