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 these techniques can prevent excessive JSON data exposure in APIs?

A) Avoiding nested JSON structures

B) Compressing JSON

C) Using JSON.stringify()

D) Enabling strict validation in APIs

2 / 30

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

A) JSON.parse()

B) JSON.stringify()

C) JSON.minify()

D) JSON.debug()

3 / 30

3. How do you merge two JSON objects?

A) Use JSON.stringify()

B) Use JSON.merge()

C) Use Object.assign()

D) Use array.push()

4 / 30

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

A) GraphQL

B) WebSockets

C) HTTP/2

D) SOAP

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5. How is JSON used in microservices architecture?

A) To exchange data between microservices

B) To compile service code

C) To define database schemas

D) To render UI components

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6. Which of the following status codes indicates a successful API request?

A) 404

B) 500

C) 403

D) 200

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7. How do you specify that a JSON object must have at least one key in JSON Schema?

A) minItems: 1

B) minProperties: 1

C) required: true

D) minKeys: 1

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8. Can JSON objects contain duplicate keys?

A) No

B) Yes, but only for strings

C) Yes, with an error

D) Yes, the last key-value pair overrides the previous ones

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

A) Object

B) String

C) Set

D) Array

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10. How does Firebase use JSON?

A) For real-time database storage and synchronization

B) To manage authentication tokens

C) To define cloud functions

D) To render user interfaces

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

A) Defining app layouts

B) Compiling source code

C) Managing memory allocation

D) Exchanging data with remote APIs

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12. How do you access the name of the first employee in the JSON structure { "department": { "employees": [ { "name": "John" }, { "name": "Alice" } ] } }?

A) employees[0].name

B) department[employees][name]

C) department.employees[0].name

D) department.employees[1].name

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

A) object.name

B) object[1]

C) object[0]

D) object["Alice"]

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

A) 1

B) true

C) null

D) "ok"

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15. What is used to enclose JSON keys?

A) Parentheses

B) Single quotes

C) Double quotes

D) No quotes

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16. What is the MIME type for JSON?

A) application/javascript

B) text/json

C) application/json

D) text/plain

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17. Can JSON keys have spaces?

A) Yes, with quotes

B) No

C) Only in arrays

D) Yes, without quotes

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18. What happens when you use JSON.stringify() on an object with a circular reference?

A) It converts the object to a string successfully

B) It throws a syntax error

C) It throws a TypeError

D) It ignores the circular reference

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

A) Only an array

B) Either an object or an array

C) Only an object

D) A string

20 / 30

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

A) Lodash

B) D3.js

C) jQuery

D) Axios

21 / 30

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

A) JSON with comments

B) Flat, simple key-value pairs

C) Deeply nested objects

D) Objects with arrays

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

A) Add a spaces property to the JSON object

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

C) Use JSON.prettyPrint()

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

23 / 30

23. How does Postman help in debugging JSON APIs?

A) It beautifies JSON data

B) It converts JSON to XML

C) It validates JSON against schemas

D) It sends requests and shows JSON responses

24 / 30

24. How are multiple key-value pairs separated in a JSON object?

A) Semicolon

B) Dot

C) Comma

D) Hyphen

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25. What happens when you pass a replacer function to JSON.stringify()?

A) Throws an error if the function is invalid

B) It filters the properties to be included in the JSON string

C) It ensures all properties are stringified

D) It validates the JSON string

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

A) DELETE

B) PUT

C) POST

D) GET

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27. What is JSON Schema?

A) A method to minify JSON files

B) A format to store JSON data

C) A library to parse JSON data

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

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28. How are elements in a JSON array separated?

A) Commas

B) Semicolons

C) Dots

D) Colons

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29. Which of these is NOT true about JSON?

A) JSON is lightweight and language-independent

B) JSON is commonly used for APIs

C) JSON supports single-line and multi-line comments

D) JSON keys must always be strings

30 / 30

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

A) To add extra spacing between keys and values

B) To format the output with indentation

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

D) To compress the JSON output

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