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 of the following is true about JSON numbers?

A) They support both integers and floats

B) They cannot be negative

C) They must include a decimal point

D) They must be enclosed in double quotes

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2. What is the primary advantage of using binary JSON formats like BSON?

A) Smaller size and faster parsing

B) Automatic validation

C) Compatibility with XML

D) Enhanced readability

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3. Which of the following values is not valid in JSON?

A) "Hello"

B) null

C) undefined

D) 123

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4. How does Elasticsearch use JSON?

A) To validate user input

B) To store and query documents

C) To define relational tables

D) To render dashboards

5 / 30

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

A) Cross-Site Scripting (XSS)

B) Remote Code Execution

C) Denial of Service (DoS)

D) SQL Injection

6 / 30

6. How can JSON responses be protected from being cached by unauthorized users?

A) Use the Cache-Control header with no-store

B) Convert JSON to XML

C) Use large nested objects

D) Minify the JSON data

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

A) {}

B) null

C) ""

D) []

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8. 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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9. What does a JSON array of objects look like?

A) [ { "key": "value" }, { "key": "value" } ]

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

C) { "object1": "value1", "object2": "value2" }

D) [ "object1", "object2" ]

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

A) A numeric range

B) A single string

C) A boolean flag

D) An array of types

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11. JSON is a strict subset of which language?

A) Python

B) JavaScript

C) XML

D) SQL

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12. What is the maximum depth for nesting in JSON?

A) 5 levels

B) 10 levels

C) Unlimited

D) Depends on the programming language and environment

13 / 30

13. What is used to enclose JSON keys?

A) Single quotes

B) Parentheses

C) Double quotes

D) No quotes

14 / 30

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

A) properties

B) format

C) items

D) type

15 / 30

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

A) JSON Flooding

B) JSON Injection

C) JSON Brute Force

D) JSON Parsing Loops

16 / 30

16. What does the properties keyword do in JSON Schema?

A) Specifies the data type of an array

B) Lists all required fields in an object

C) Defines the keys allowed in an object

D) Defines the maximum number of keys in an object

17 / 30

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

A) [1, 2, null, 4]

B) Throws a SyntaxError

C) [1, 2, , 4]

D) [1, 2, undefined, 4]

18 / 30

18. Which of the following tools can debug REST API calls and their JSON responses?

A) JSONLint

B) Postman

C) Notepad++

D) Visual Studio Code

19 / 30

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

A) String

B) Number

C) Object

D) Array

20 / 30

20. What is the purpose of an API key in requests?

A) To encrypt the request data

B) To indicate the request priority

C) To specify the API version

D) To authenticate the client

21 / 30

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

A) To parse JSON strings

B) To make HTTP requests to APIs

C) To send emails

D) To encrypt data

22 / 30

22. Which method is used to convert a JavaScript object into a JSON string?

A) JSON.parse()

B) JSON.encode()

C) JSON.toString()

D) JSON.stringify()

23 / 30

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

A) "Hello"

B) 'Hello'

C) Hello

D) “Hello”

24 / 30

24. Which JavaScript method can convert an object into a JSON string for an API request?

A) JSON.serialize()

B) JSON.parse()

C) JSON.encode()

D) JSON.stringify()

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

A) Use Array.isArray()

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

C) Use Object.prototype.toString()

D) Use typeof to check if it is an object

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26. Which of the following methods can help trace JSON parsing errors in JavaScript?

A) console.parse()

B) try...catch blocks around JSON.parse()

C) JSON.log()

D) window.debug()

27 / 30

27. How does Firebase use JSON?

A) To define cloud functions

B) For real-time database storage and synchronization

C) To render user interfaces

D) To manage authentication tokens

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28. Which of the following is a valid JSON array?

A) [1; 2; 3]

B) (1, 2, 3)

C) [1, 2, "three"]

D) {"1", "2", "3"}

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29. Which tool can be used to measure JSON parsing performance in JavaScript?

A) JSON Formatter

B) JSON Schema Validator

C) Chrome DevTools

D) JSONLint

30 / 30

30. 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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