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

A) JSON Formatter

B) Chrome DevTools

C) JSON Schema Validator

D) JSONLint

2 / 30

2. Which of the following is an example of a valid JSON number?

A) Both B and C

B) 123.45

C) "123"

D) 123

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

A) type

B) properties

C) items

D) format

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4. Which of the following is a common use of JSON in web development?

A) Compiling JavaScript code

B) Storing and exchanging data between client and server

C) Defining CSS styles

D) Rendering HTML elements

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5. How is JSON used in microservices architecture?

A) To exchange data between microservices

B) To render UI components

C) To compile service code

D) To define database schemas

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

A) JSON.log()

B) window.debug()

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

D) console.parse()

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7. Which data structure is JSON closest to?

A) Arrays

B) Relational tables

C) Key-value store

D) Trees

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

A) object[1]

B) object[0]

C) object.name

D) object["Alice"]

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

A) Converting JavaScript objects into readable JSON format

B) Formatting JSON output with indentation

C) Serializing objects with circular references

D) Serializing objects for storage or transmission

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10. Which browser's developer tools are commonly used to debug JSON in web applications?

A) Firefox

B) Internet Explorer

C) Safari

D) Google Chrome

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

A) min and max

B) numberRange

C) range

D) minimum and maximum

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

A) "Hello"

B) 123

C) undefined

D) null

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

A) "1.23"

B) 1.23

C) 1.23f

D) float(1.23)

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

A) Avoid logging altogether

B) Use JSON.stringify()

C) Use a secure logging framework and mask sensitive data

D) Log the raw JSON data as is

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15. What happens when duplicate keys are present in a JSON object?

A) Both key-value pairs are stored

B) An error is thrown

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

D) The first key-value pair is ignored

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16. How does Firebase use JSON?

A) For real-time database storage and synchronization

B) To manage authentication tokens

C) To render user interfaces

D) To define cloud functions

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

A) String

B) Object

C) Array

D) Null

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

A) Denial of Service (DoS)

B) Remote Code Execution

C) SQL Injection

D) Cross-Site Scripting (XSS)

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

A) Checking the JSON string with isValid()

B) JSON parsing cannot produce errors

C) Using the JSON.validate() method

D) Using a try...catch block

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

A) JSON.minify()

B) JSON.parse()

C) JSON.debug()

D) JSON.stringify()

21 / 30

21. Which messaging protocol often uses JSON for message payloads?

A) MQTT

B) FTP

C) POP3

D) SMTP

22 / 30

22. What is the MIME type for JSON?

A) application/javascript

B) text/plain

C) text/json

D) application/json

23 / 30

23. Which keyword restricts the number of items in a JSON array?

A) minLength

B) maxItems

C) maxSize

D) arrayLimit

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24. Can JSON arrays contain objects?

A) No

B) Only numbers

C) Only strings

D) Yes

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25. How do you merge two JSON objects?

A) Use array.push()

B) Use JSON.stringify()

C) Use JSON.merge()

D) Use Object.assign()

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26. Which of the following formats can JSON be easily converted into for data visualization?

A) All of the above

B) HTML

C) CSV

D) XML

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27. How do you identify invalid JSON in a web application?

A) Use the browser's developer tools

B) All of the above

C) Log errors in the console

D) Use a linter or formatter tool

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28. What does the package.json file in a Node.js project contain?

A) A list of all JavaScript files

B) The project's HTML templates

C) Metadata about the project, dependencies, and scripts

D) The project's CSS styles

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

A) Object

B) Array

C) String

D) Number

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

A) jQuery

B) Axios

C) Lodash

D) D3.js

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