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 happens when duplicate keys are present in a JSON object?

A) An error is thrown

B) The last key-value pair overrides the previous ones

C) The first key-value pair is ignored

D) Both key-value pairs are stored

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

A) JSON.serialize()

B) JSON.stringify()

C) JSON.parse()

D) JSON.encode()

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3. What can be the root structure of a JSON document?

A) A string

B) Only an object

C) Only an array

D) Either an object or an array

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4. Which function can convert an API response from JSON to JavaScript objects?

A) response.parse()

B) JSON.stringify()

C) JSON.decode()

D) response.json()

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5. How do you handle errors in a fetch() request?

A) Using fetchError() function

B) Using the error property of the response

C) Errors cannot be handled in fetch()

D) Using try...catch blocks or then().catch() methods

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

A) Use JSON.prettyPrint()

B) Add a spaces property to the JSON object

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

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

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7. 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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8. What is the maximum depth for nesting in JSON?

A) 5 levels

B) 10 levels

C) Depends on the programming language and environment

D) Unlimited

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9. What is the best approach to log sensitive information within JSON responses?

A) Avoid logging altogether

B) Use a secure logging framework and mask sensitive data

C) Use JSON.stringify()

D) Log the raw JSON data as is

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

A) Throws an error

B) A deep copy of the object

C) A string representation of the nested object

D) A flattened version of the object

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12. Which of the following is NOT a supported data type in JSON?

A) Undefined

B) String

C) Boolean

D) Number

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

A) Objects with arrays

B) JSON with comments

C) Flat, simple key-value pairs

D) Deeply nested objects

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14. How is JSON used in microservices architecture?

A) To render UI components

B) To compile service code

C) To exchange data between microservices

D) To define database schemas

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15. What is a safe alternative to eval() for parsing JSON in JavaScript?

A) JSON.stringify()

B) JSON.debug()

C) JSON.parse()

D) JSON.minify()

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

A) String

B) All of the above

C) Object

D) Float

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

A) Managing memory allocation

B) Exchanging data with remote APIs

C) Compiling source code

D) Defining app layouts

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

A) Numbers

B) Comments

C) Strings

D) Boolean values

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

A) It provides a lightweight and flexible data format

B) It is faster than wireless communication

C) It reduces power consumption

D) It encrypts all data automatically

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

A) Remote Code Execution

B) SQL Injection

C) Cross-Site Scripting (XSS)

D) Denial of Service (DoS)

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21. What will be the output of the code: JSON.stringify({ key1: "value1", key2: function() { return "value2"; } });

A) {"key1": "value1", "key2": "value2"}

B) {"key1": "value1"}

C) Throws an error

D) {"key1": "value1", "key2": null}

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

A) Converts a JavaScript object into a JSON string

B) Converts a JSON string into a JavaScript object

C) Parses a JSON string into an XML object

D) Validates a JSON string

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

A) JSON Formatter

B) JSONLint

C) Postman

D) jq

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

A) WebSockets

B) HTTP/2

C) GraphQL

D) SOAP

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

A) name

B) "123name"

C) "_name"

D) "name!"

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

A) SQLite

B) MySQL

C) MongoDB

D) PostgreSQL

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27. What symbol is used to enclose a JSON array?

A) <>

B) []

C) {}

D) ()

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

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

B) [1, 2, "three"]

C) [1; 2; 3]

D) (1, 2, 3)

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29. What is the potential issue with using eval() to parse JSON strings in JavaScript?

A) It cannot parse valid JSON strings

B) Slower parsing

C) Increased memory usage

D) Vulnerability to code injection attacks

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30. What type of data does a JSON object contain?

A) Key-value pairs

B) Only numbers

C) Only arrays

D) Only text

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