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

A) properties: []

B) additionalFields: false

C) maxProperties: 0

D) additionalProperties: false

2 / 30

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

A) Number

B) String

C) Array

D) Object

3 / 30

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

A) Set

B) Object

C) Array

D) String

4 / 30

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

A) object.name

B) object[0]

C) object["Alice"]

D) object[1]

5 / 30

5. Which of these is NOT allowed in JSON arrays?

A) Nested arrays

B) Functions as elements

C) Mixed data types

D) Objects as elements

6 / 30

6. How does Postman help in debugging JSON APIs?

A) It beautifies JSON data

B) It validates JSON against schemas

C) It converts JSON to XML

D) It sends requests and shows JSON responses

7 / 30

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

A) The project's CSS styles

B) A list of all JavaScript files

C) The project's HTML templates

D) Metadata about the project, dependencies, and scripts

8 / 30

8. What is the purpose of the fetch() method in JavaScript?

A) To encrypt data

B) To make HTTP requests to APIs

C) To send emails

D) To parse JSON strings

9 / 30

9. What does a JSON path debugger do?

A) Extracts specific values from JSON

B) Validates JSON syntax

C) Beautifies JSON

D) Converts JSON to CSV

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

A) Use parent() function

B) Use a library to navigate JSON paths

C) Use key.parent

D) JSON does not support parent references

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11. How can you identify unused keys in a JSON object?

A) Postman

B) Static analysis tools or manual comparison

C) JSON Formatter

D) JSONLint

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

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

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

C) Use JSON.prettyPrint()

D) Add a spaces property to the JSON object

13 / 30

13. Which keyword specifies the schema for items in a JSON array?

A) definitions

B) properties

C) items

D) type

14 / 30

14. What does the Content-Security-Policy header do for JSON responses?

A) Ensures JSON is minified

B) Defines the format of JSON data

C) Specifies how JSON is cached

D) Restricts where JSON can be loaded from to prevent cross-site scripting (XSS) attacks

15 / 30

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

A) Numbers

B) Strings

C) Comments

D) Boolean values

16 / 30

16. Which JSON data type is used to group key-value pairs?

A) Array

B) Object

C) String

D) Number

17 / 30

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

A) Defines the keys allowed in an object

B) Specifies the data type of an array

C) Defines the maximum number of keys in an object

D) Lists all required fields in an object

18 / 30

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

A) window.debug()

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

C) console.parse()

D) JSON.log()

19 / 30

19. Which of the following is the correct way to represent an empty JSON object?

A) {}

B) ""

C) null

D) []

20 / 30

20. What is the primary function of JSON.stringify(value, replacer, space)?

A) Converts an object to a string with formatting options

B) Converts JSON to XML

C) Compresses JSON output

D) Beautifies JSON output

21 / 30

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

A) []

B) {}

C) <>

D) ()

22 / 30

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

A) The key must be enclosed in double quotes

B) The key is ignored

C) The special characters are escaped automatically

D) It throws an error

23 / 30

23. Can JSON values be functions?

A) Only in objects

B) Only in arrays

C) Yes

D) No

24 / 30

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

A) Unlimited

B) 5 levels

C) Depends on the programming language and environment

D) 10 levels

25 / 30

25. How does JSON.stringify() handle functions in objects?

A) Functions are converted to strings

B) Adds null in place of functions

C) Throws an error

D) Functions are ignored

26 / 30

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

A) POP3

B) MQTT

C) FTP

D) SMTP

27 / 30

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

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

B) Use Object.prototype.toString()

C) Use Array.isArray()

D) Use typeof to check if it is an object

28 / 30

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

A) Object

B) Null

C) Array

D) String

29 / 30

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

A) Vulnerability to code injection attacks

B) Slower parsing

C) It cannot parse valid JSON strings

D) Increased memory usage

30 / 30

30. What does a JSON Formatter do?

A) Formats JSON into a readable and indented structure

B) Parses JSON into JavaScript objects

C) Converts JSON to XML

D) Compresses JSON into a single line

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