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.

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

A) Use Array.isArray()

B) Use typeof to check if it is an object

C) Use Object.prototype.toString()

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

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2. Which online tool is commonly used to format JSON for readability?

A) Visual Studio Code

B) JSONLint

C) Postman

D) GitHub

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3. What is the output of JSON.stringify() on a nested object?

A) A flattened version of the object

B) A string representation of the nested object

C) A deep copy of the object

D) Throws an error

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

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

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

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

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

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

A) HTTP/2

B) SOAP

C) GraphQL

D) WebSockets

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

A) MySQL

B) SQLite

C) MongoDB

D) PostgreSQL

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

A) To define the schema

B) To manage subscriptions

C) To handle authentication

D) To format query results

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8. What happens if a key in a JSON object contains special characters?

A) The key must be enclosed in double quotes

B) The special characters are escaped automatically

C) It throws an error

D) The key is ignored

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9. Which of the following is NOT a valid use case of JSON.stringify()?

A) Serializing objects for storage or transmission

B) Converting JavaScript objects into readable JSON format

C) Serializing objects with circular references

D) Formatting JSON output with indentation

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10. What is the result of JSON.parse('null') in JavaScript?

A) Throws a syntax error

B) Converts to the string "null"

C) Returns null

D) Returns undefined

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11. Which of these is a valid JSON object?

A) {name = "John"; age = 30}

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

C) [name: "John", age: 30]

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

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12. Which of the following is NOT a valid JSON key?

A) name

B) "_name"

C) "123name"

D) "name!"

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

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

B) window.debug()

C) JSON.log()

D) console.parse()

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

A) jQuery

B) Lodash

C) D3.js

D) Axios

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

A) additionalFields: false

B) additionalProperties: false

C) properties: []

D) maxProperties: 0

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

A) Specifies the data type of an array

B) Defines the maximum number of keys in an object

C) Defines the keys allowed in an object

D) Lists all required fields in an object

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17. What does the Content-Type header specify in an API request?

A) The size of the request body

B) The format of the data being sent or expected

C) The HTTP method to be used

D) The status of the response

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18. How can you handle errors when parsing JSON in JavaScript?

A) Using the JSON.validate() method

B) Checking the JSON string with isValid()

C) JSON parsing cannot produce errors

D) Using a try...catch block

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19. How do you specify a pattern for a string in JSON Schema?

A) match

B) regex

C) pattern

D) format

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

A) Input validation and sanitization

B) Using only numeric data

C) Removing all keys from JSON

D) Minification

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

A) "null"

B) NULL

C) null

D) (null)

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23. How can large nested JSON objects impact performance?

A) They reduce API latency

B) They slow down parsing and increase memory usage

C) They make JSON more secure

D) They improve network speed

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24. In which cloud service is JSON commonly used for defining infrastructure as code?

A) Firebase

B) DigitalOcean

C) Microsoft Azure

D) Amazon Web Services (AWS) CloudFormation

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

A) Postman

B) JSONLint

C) JSON Formatter

D) jq

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26. How does Elasticsearch use JSON?

A) To validate user input

B) To define relational tables

C) To render dashboards

D) To store and query documents

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

A) null

B) true

C) "ok"

D) 1

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29. What does a 404 status code signify in an API response?

A) Unauthorized access

B) Resource not found

C) Internal server error

D) Bad request

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30. What is the advantage of using JSON in IoT (Internet of Things) devices?

A) It is faster than wireless communication

B) It encrypts all data automatically

C) It provides a lightweight and flexible data format

D) It reduces power consumption

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