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 can JSON responses be protected from being cached by unauthorized users?

A) Use the Cache-Control header with no-store

B) Convert JSON to XML

C) Use large nested objects

D) Minify the JSON data

2 / 30

2. How do you merge two JSON objects?

A) Use JSON.stringify()

B) Use JSON.merge()

C) Use Object.assign()

D) Use array.push()

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3. 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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4. Which of the following JSON data types is valid?

A) All of the above

B) Float

C) Object

D) String

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5. How can you debug a failing JSON API request in a browser?

A) Validate the response JSON using a linter

B) Use console.log for JSON output

C) All of the above

D) Check the network tab in developer tools

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6. Which data structure is JSON closest to?

A) Arrays

B) Relational tables

C) Trees

D) Key-value store

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

A) Set

B) Array

C) Object

D) String

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

A) JSON Compressor

B) JSON Beautifier

C) JSON Validator

D) JSON Formatter

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10. Why should large JSON files be paginated in APIs?

A) To increase readability

B) To avoid key duplication

C) To reduce client-side processing time

D) To improve network performance and reduce latency

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11. What is the correct syntax for a JSON object?

A) {"key": "value"}

B) [key: "value"]

C) {key: "value"}

D) {key = "value"}

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12. From which programming language is JSON derived?

A) C++

B) Java

C) JavaScript

D) Python

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

A) Objects as elements

B) Functions as elements

C) Mixed data types

D) Nested arrays

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

A) Flat, simple key-value pairs

B) JSON with comments

C) Objects with arrays

D) Deeply nested objects

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15. Which of the following is an invalid JSON structure?

A) { "key": { "nested": { "deep": [1, 2] } } }

B) [ { "key1": "value1" }, { "key2": "value2" } ]

C) { "key": [1, 2, { "nested": "value" }] }

D) { "key": "value", "key": "anotherValue" }

16 / 30

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

A) min and max

B) range

C) minimum and maximum

D) numberRange

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17. JSON is a strict subset of which language?

A) JavaScript

B) SQL

C) Python

D) XML

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18. What is JSON primarily used for?

A) Sending emails

B) Data exchange between a client and a server

C) Creating animations

D) Styling web pages

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19. Why is it important to validate JSON data received from external sources?

A) To improve parsing speed

B) To convert JSON into JavaScript objects

C) To compress JSON

D) To prevent unexpected errors and security vulnerabilities

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

A) Semicolon

B) Dot

C) Comma

D) Hyphen

21 / 30

21. What is the purpose of JSON in REST APIs?

A) To define API endpoints

B) To structure and exchange data between client and server

C) To validate API responses

D) To render HTML pages

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22. Which of these is a valid JSON array of strings?

A) ['apple', 'banana', 'cherry']

B) [apple, banana, cherry]

C) ["apple", 'banana', "cherry"]

D) ["apple", "banana", "cherry"]

23 / 30

23. What is the output of the code: JSON.stringify({ key: undefined, key2: "value" });

A) {"key2": "value"}

B) {"key": undefined, "key2": "value"}

C) {"key": "", "key2": "value"}

D) {"key": null, "key2": "value"}

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24. How do you represent a key-value pair where the value is an array?

A) { "key": { "value1": "value2" } }

B) { "key": "value1", "value2" }

C) { "key": [ "value1", "value2" ] }

D) [ { "key": "value1" } ]

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

A) properties: []

B) maxProperties: 0

C) additionalFields: false

D) additionalProperties: false

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

A) Depends on the programming language and environment

B) Unlimited

C) 5 levels

D) 10 levels

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27. What does the type keyword accept for mixed data types?

A) A single string

B) A boolean flag

C) A numeric range

D) An array of types

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

A) All of the above

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

C) [ "Alice", 25, true ]

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

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29. Which method can be used to transform a JSON object into an iterable array?

A) Object.entries()

B) Object.keys()

C) All of the above

D) Object.values()

30 / 30

30. Which of the following is a valid JSON string?

A) "Hello"

B) 'Hello'

C) “Hello”

D) Hello

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