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 is JSON primarily used for?

A) Styling web pages

B) Sending emails

C) Creating animations

D) Data exchange between a client and a server

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2. How can you validate JSON in a secure and efficient way?

A) Ignore validation for trusted sources

B) Manually check the JSON

C) Use a JSON Schema validator

D) Use custom regular expressions

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

A) Use Object.prototype.toString()

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

C) Use typeof to check if it is an object

D) Use Array.isArray()

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

A) Lists all required fields in an object

B) Defines the keys allowed in an object

C) Specifies the data type of an array

D) Defines the maximum number of keys in an object

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5. What is the purpose of the space parameter in JSON.stringify()?

A) To compress the JSON output

B) To add a specific number of spaces to the start of the output

C) To format the output with indentation

D) To add extra spacing between keys and values

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6. What data type is represented by {} in JSON?

A) Null

B) Array

C) String

D) Object

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

A) JSON.minify()

B) JSON.parse()

C) JSON.stringify()

D) JSON.debug()

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8. Which of the following is valid JSON for a mixed data type array?

A) All of the above

B) [ "Alice", 25, true ]

C) [ { "name": "Alice" }, 25, "true" ]

D) [ "Alice", "25", true ]

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9. Which HTTP method is commonly used to fetch JSON data from an API?

A) POST

B) GET

C) DELETE

D) PUT

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10. What error does a missing comma between JSON key-value pairs produce?

A) Invalid JSON

B) SyntaxError: Unexpected token

C) Undefined object

D) Missing property name

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11. How does JSON web encryption (JWE) enhance JSON security?

A) It adds authentication to JSON

B) It compresses JSON data

C) It encrypts JSON payloads for secure transmission

D) It converts JSON to binary format

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12. How is JSON used in microservices architecture?

A) To compile service code

B) To exchange data between microservices

C) To render UI components

D) To define database schemas

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13. What is the purpose of the additionalProperties keyword?

A) To specify array constraints

B) To validate nested objects

C) To define extra fields that are allowed in an object

D) To allow duplicate keys in an object

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

A) ReferenceError

B) A key-value pair object

C) null

D) SyntaxError: Unexpected identifier

15 / 30

15. What is JSON Schema?

A) A library to parse JSON data

B) A format to store JSON data

C) A method to minify JSON files

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

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

A) Using the error property of the response

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

C) Errors cannot be handled in fetch()

D) Using fetchError() function

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17. Which keyword is used to specify required fields in a JSON object?

A) required

B) mandatory

C) fields

D) include

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18. Which keyword defines a numeric range in JSON Schema?

A) numberRange

B) minimum and maximum

C) min and max

D) range

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19. Which of the following is used to validate the syntax of JSON data?

A) JSON Compressor

B) JSON Beautifier

C) JSON Formatter

D) JSON Validator

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

A) JSONLint

B) Chrome DevTools

C) JSON Formatter

D) JSON Schema Validator

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

A) [1, 2, undefined, 4]

B) [1, 2, , 4]

C) [1, 2, null, 4]

D) Throws a SyntaxError

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22. What is the effect of caching JSON responses?

A) Increases JSON size

B) Prevents JSON injection attacks

C) Converts JSON to binary format

D) Reduces server processing time for repeated requests

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23. How do you reference the parent key in a deeply nested JSON object?

A) Use a library to navigate JSON paths

B) Use key.parent

C) Use parent() function

D) JSON does not support parent references

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24. What is the output of JSON.stringify([1, undefined, 2])?

A) "[1, null, 2]"

B) "[1, undefined, 2]"

C) "[1, , 2]"

D) Throws a TypeError

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25. Which of these is a valid boolean value in JSON?

A) true

B) "true"

C) True

D) TRUE

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

A) 5 levels

B) Unlimited

C) Depends on the programming language and environment

D) 10 levels

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27. What does the Accept header specify in an API request?

A) The server's API version

B) The authentication type

C) The client type

D) The data format expected in the response

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

A) "1.23"

B) float(1.23)

C) 1.23f

D) 1.23

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29. How is JSON used in data interchange for machine learning models?

A) To render visualizations

B) To compile machine learning libraries

C) To serialize model configurations and results

D) To train models directly

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30. What is the most efficient way to handle large JSON datasets in memory-constrained environments?

A) Use streaming APIs to process JSON incrementally

B) Remove all nested objects

C) Convert JSON to XML first

D) Load the entire JSON at once

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